Intermediate film for laminated glass and laminated glass

ABSTRACT

The present invention provides an interlayer film for laminated glass having a monolayer structure comprising only a first layer or a multilayer structure comprising at least two layers including a first layer and a second layer stacked at least on one face of the first layer, wherein the first layer contains a thermoplastic resin and a first plasticizer represented by the formula (1): 
     
       
         
         
             
             
         
       
     
     and the interlayer film has a monolayer structure or a multilayer structure including at least two layers and includes the first layer further containing a second plasticizer that is a diester compound, or the interlayer film has a multilayer structure including at least two layers and includes the second layer containing a plasticizer and a polyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of patent applicationSer. No. 13/809,885, filed on Feb. 28, 2013, which is a 371 applicationof Application No. PCT/JP2011/066247, filed on Jul. 15, 2011, which isbased on Japanese Application Nos. 2010-161617 and 2010-161618 filed onJul. 16, 2010, and 2011-144863 filed on Jun. 29, 2011, the entirecontents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an interlayer film for laminated glasscontaining a thermoplastic resin and a plasticizer. More specifically,the present invention relates to an interlayer film for laminated glasswhich can provide a laminated glass excellent in sound insulation, andalso relates to a laminated glass produced using the interlayer film forlaminated glass.

BACKGROUND ART

A laminated glass is a safety glass because few glass fragments arescattered even if it is broken by impact from the outside. Therefore,the laminated glass has been used widely for automobiles, railway cars,aircrafts, vessels, buildings, and the like. The laminated glass has aninterlayer film interposed between a pair of glass sheets.

Recently, reduction in thickness of the laminated glass has beenconsidered for weight reduction of the laminated glass. Reduction inthickness of the laminated glass however causes deterioration in soundinsulation of the laminated glass. Use of the laminated glass with poorsound insulation as windshields of automobiles may problematicallyresult in insufficient sound insulation for sound with a frequency ofabout 5000 Hz such as whizzing sound and driving sound of windshieldwipers.

Change in materials of interlayer films is now considered to increasethe sound insulation of the laminated glass.

Patent Document 1 provides one example of the interlayer film forlaminated glass; that is, Patent Document 1 teaches a sound insulationlayer that contains 100 parts by weight of a polyvinyl acetal resinhaving an acetalization degree of 60 to 85 mol %, 0.001 to 1.0 part byweight of at least one metal salt of alkali metal salts and alkalineearth metal salts, and 30 parts by weight or more of a plasticizer. Thissound insulation layer can be used alone as an interlayer film, or usedas a multilayer interlayer film in the form of a stack with otherlayer(s).

-   Patent Document 1: JP 2007-070200 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Though a laminated glass including an interlayer film disclosed inPatent Document 1 can increase the sound insulation to some degree,further increase in the sound insulation is now required.

The sound to be insulated by the interlayer film includes air-bornesound such as vehicle noises and horns, and solid born sound such asvibrations of vehicle engines. The laminated glass including aninterlayer film disclosed in Patent Document 1 may fail to sufficientlyincrease the sound insulation especially for solid born sound.

Meanwhile, considerations have been made in recent years to add anexcessive amount of a plasticizer to an interlayer film for increasingthe sound insulation of a laminated glass. Addition of an excessiveamount of a plasticizer can improve the sound insulation of thelaminated glass. However, an excessive amount of the plasticizersometimes causes bleeding of the plasticizer on the surface of theinterlayer film and bubble formation in the laminated glass.

The present invention aims to provide an interlayer film for laminatedglass which can give a laminated glass with better sound insulation whenused in the laminated glass; and a laminated glass using the interlayerfilm for laminated glass.

The present invention limitedly aims to provide an interlayer film forlaminated glass which can give a laminated glass with better soundinsulation and better penetration resistance when used in the laminatedglass; and a laminated glass using the interlayer film for laminatedglass.

The present invention further limitedly aims to provide an interlayerfilm for laminated glass which can give a laminated glass that is notonly excellent in the sound insulation but also capable of suppressingbubble formation and bubble growth; and a laminated glass using theinterlayer film for laminated glass.

Means for Solving the Problems

According to a broad aspect of the present invention, the presentinvention provides an interlayer film for laminated glass having amonolayer structure comprising only a first layer or a multilayerstructure comprising at least two layers including a first layer and asecond layer stacked at least on one face of the first layer, whereinthe first layer contains a thermoplastic resin and a first plasticizerrepresented by the formula (1), and the interlayer film has a monolayerstructure or a multilayer structure including at least two layers andincludes the first layer further containing a second plasticizer that isa diester compound, or the interlayer film has a multilayer structureincluding at least two layers and includes the second layer containing aplasticizer and a polyvinyl acetal resin with a hydroxyl content of 25to 40 mol %.

In the formula (1), R1 and R2 each represent an organic group containingat least one ether bond and n represents an integer of 2 to 8.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, R1 and R2 in the formula (1) eachrepresent a group containing a carbon atom and an oxygen atom in a totalnumber of at most 12.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, R1 and R2 in the formula (1) each haveat least one ether bond structural unit represented by the formula (11)or the formula (12).

According to a specific aspect of the interlayer film for laminatedglass of the present invention, R1 is a group represented by the formula(21) and R2 is a group represented by the formula (26) in the formula(1).

In the formula (21), R21 represents an alkyl group having 1 to 10 carbonatom(s), R22 represents an alkylene group having 1 to 10 carbon atom(s),and m1 represents an integer of 1 to 5.

In the formula (26), R26 represents an alkyl group having 1 to 10 carbonatom(s), R27 represents an alkylene group having 1 to 10 carbon atom(s),and m2 represents an integer of 1 to 5.

When the interlayer film has a monolayer structure or a multilayerstructure including at least two layers and includes the first layerfurther containing a second plasticizer that is a diester compound, thesecond plasticizer is preferably represented by the formula (51).

In the formula (51), R51 and R52 each represent an organic group having5 to 10 carbon atoms, R53 represents an ethylene group, isopropylenegroup or n-propylene group, and p represents an integer of 3 to 10.

When the interlayer film has a monolayer structure or a multilayerstructure including at least two layers and includes the first layerfurther containing a second plasticizer that is a diester compound, thefirst layer preferably contains the first plasticizer and the secondplasticizer at a weight ratio of 1:9 to 8.5:1.5.

When the interlayer film has a multilayer structure including at leasttwo layers and includes the second layer containing a plasticizer and apolyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %, theplasticizer in the second layer is preferably a second plasticizer thatis a diester compound. The second plasticizer that is a diester compoundin the second layer is preferably a second plasticizer represented bythe formula (51).

When the interlayer film has a multilayer structure including at leasttwo layers and includes the second layer containing a plasticizer and apolyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %, thefirst layer further preferably contains a second plasticizer that is adiester compound. The second plasticizer that is a diester compound inthe first layer is second plasticizer represented by the formula (51).

when the interlayer film has a multilayer structure including at leasttwo layers and includes the second layer containing a plasticizer and apolyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %, thefirst layer preferably further contains a second plasticizer that is adiester compound and the first layer preferably contains the firstplasticizer and the second plasticizer at a weight ratio of 1:9 to8.5:1.5.

When the interlayer film has a multilayer structure including at leasttwo layers and includes the second layer containing a plasticizer and apolyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %, thepolyvinyl acetal resin in the second layer preferably has an acetalgroup with 3 or 4 carbon atoms, an acetalization degree of 60 to 75 mol%, and an acetylation degree of 0 to 10 mol %.

The thermoplastic resin in the first layer is preferably a polyvinylacetal resin. The polyvinyl acetal resin in the first layer preferablyhas a hydroxyl content of at most 25 mol %.

The polyvinyl acetal resin in the first layer is preferably obtained byacetalization of a polyvinyl alcohol having an average degree ofpolymerization of 2700 to 5000.

In a yet another specific aspect of the interlayer film for laminatedglass according to the present invention, the thermoplastic resin in thefirst layer contains a high molecular weight component having anabsolute molecular weight of at least 1 million and the high molecularweight component accounts for at least 7.4% of the thermoplastic resinin the first layer, or the thermoplastic resin in the first layercontains a high molecular weight component having apolystyrene-equivalent molecular weight of at least 1 million and thehigh molecular weight component accounts for at least 9% of thethermoplastic resin in the first layer.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, when the first layer is used as a resinfilm with a glass transition temperature of Tg (° C.) for measurement ofthe viscoelasticity, an elasticity G′(Tg+80) at (Tg+80)° C. and anelasticity G′(Tg+30) at (Tg+30)° C. have a ratio (G′(Tg+80)/G′(Tg+30))of at least 0.65.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the thermoplastic resin in the firstlayer is a polyvinyl acetal resin, and when the viscoelasticity of aresin film containing 100 parts by weight of the polyvinyl acetal resinin the first layer and 60 parts by weight of triethylene glycoldi-2-ethylhexanoate (3GO) as a plasticizer and having a glass transitiontemperature of Tg (° C.) for measurement of the viscoelasticity, anelasticity G′(Tg+80) at (Tg+80)° C. and an elasticity G′(Tg+30) at(Tg+30)° C. have a ratio (G′(Tg+80)/G′ (Tg+30)) of at least 0.65.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the thermoplastic resin in the firstlayer is a polyvinyl acetal resin, and the polyvinyl acetal resin in thefirst layer is obtained by acetalization of a polyvinyl alcohol resinhaving an average degree of polymerization of more than 3000.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the thermoplastic resin in the firstlayer is preferably a polyvinyl acetal resin, and the polyvinyl acetalresin in the first layer preferably has an acetylation degree of atleast 8 mol %, or an acetylation degree of less than 8 mol % and anacetalization degree of at least 68 mol %. The polyvinyl acetal resin inthe first layer preferably has an acetylation degree of at least 8 mol%. The polyvinyl acetal resin in the first layer preferably has anacetylation degree of less than 8 mol % and an acetalization degree ofat least 68 mol %.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the interlayer film has a monolayerstructure or a multilayer structure including at least two layers, andthe interlayer film includes the first layer containing thethermoplastic resin, the first plasticizer represented by the formula(1), and the second plasticizer that is a diester compound.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the interlayer film has a monolayerstructure, and the interlayer film includes the first layer containingthe thermoplastic resin, the first plasticizer represented by theformula (1), and the second plasticizer that is a diester compound.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the interlayer film has a multilayerstructure including at least two layers, and the interlayer filmincludes the first layer containing the thermoplastic resin, the firstplasticizer represented by the formula (1), and the second plasticizerthat is a diester compound, and the second layer stacked at least on oneface of the first layer.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the interlayer film has a multilayerstructure including at least two layers, and the interlayer filmincludes the first layer containing the thermoplastic resin and thefirst plasticizer represented by the formula (1), and the second layerthat is stacked at least on one face of the first layer and contains theplasticizer and the polyvinyl acetal resin with a hydroxyl content of 25to 40 mol %.

According to a specific aspect of the interlayer film for laminatedglass of the present invention, the interlayer film has a multilayerstructure including at least two layers, the thermoplastic resin in thefirst layer is a polyvinyl acetal resin, the second layer contains apolyvinyl acetal resin, the amount of the plasticizer is at least 50parts by weight for 100 parts by weight of the polyvinyl acetal resin inthe first layer, a hydroxyl content in the polyvinyl acetal resin in thefirst layer is lower than a hydroxyl content in the polyvinyl acetalresin in the second layer, a difference in the hydroxyl content is atmost 9.2 mol % between the polyvinyl acetal resin in the first layer andthe polyvinyl acetal resin in the second layer, and the polyvinyl acetalresin in the first layer has an acetylation degree of at most 8 mol %when the difference in the hydroxyl content is more than 8.5 mol % andat most 9.2 mol % between the polyvinyl acetal resin in the first layerand the polyvinyl acetal resin in the second layer.

A laminated glass according to the present invention comprises: a firstcomponent for laminated glass; a second component for laminated glass;an interlayer film between the first component for laminated glass andthe second component for laminated glass, wherein the interlayer filmhaving a monolayer structure or a multilayer structure includes theinterlayer film for laminated glass according to the present invention.

Effect of the Invention

An interlayer film for laminated glass according to the presentinvention has a monolayer structure or a multilayer structure includingat least two layers, wherein the first layer contains a thermoplasticresin and a first plasticizer represented by the formula (1) and theinterlayer film has a monolayer structure or a multilayer structureincluding at least two layers and includes the first layer furthercontaining a second plasticizer that is a diester compound, or theinterlayer film has a multilayer structure including at least two layersand includes the second layer containing a plasticizer and a polyvinylacetal resin with a hydroxyl content of 25 to 40 mol %. Therefore, theinterlayer film for laminated glass according to the present inventioncan increase the sound insulation of the laminated glass.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially notched cross-sectional view schematicallyillustrating an interlayer film for laminated glass according to a firstembodiment of the present invention.

FIG. 2 is a partially notched cross-sectional view schematicallyillustrating an interlayer film for laminated glass according to asecond embodiment of the present invention.

FIG. 3 is a partially notched cross-sectional view schematicallyillustrating one example of a laminated glass including the interlayerfilm for laminated glass illustrated in FIG. 1.

FIG. 4 is a partially notched cross-sectional view schematicallyillustrating one example of a laminated glass including the interlayerfilm for laminated glass illustrated in FIG. 2.

FIG. 5 is a view for illustrating a relation between the loss factor tanδ and the temperature and a relation between the elasticity G′ and thetemperature in measurement of the viscoelasticity of a resin filmcontaining a polyvinyl acetal resin in the first layer andtriethyleneglycol di-2-ethylhexanoate.

MODE(S) FOR CARRYING OUT THE INVENTION

The present invention is specifically described in the following.

The interlayer film for laminated glass according to the presentinvention has a monolayer structure including only a first layer or amultilayer structure including at least two layers of a first layer anda second layer stacked at least on one face of the first layer. Theinterlayer film for laminated glass according to the present inventionincludes the first layer containing a thermoplastic resin and a firstplasticizer represented by the formula (1).

The interlayer film for laminated glass according to the presentinvention may be a monolayer interlayer film for laminated glass havingonly the first layer. Or alternatively, the interlayer film forlaminated glass according to the present invention may be a multilayerinterlayer film for laminated glass having the first layer and thesecond layer.

The interlayer film for laminated glass according to the presentinvention includes the first layer containing a thermoplastic resin anda first plasticizer represented by the formula (1).

The interlayer film for laminated glass according to the presentinvention has a monolayer structure or a multilayer structure includingat least two layers and includes the first layer containing a secondplasticizer that is a diester compound (pattern (i)). Alternatively, theinterlayer film for laminated glass according to the present inventionhas a multilayer structure including at least two layers and includesthe second layer containing a plasticizer and a polyvinyl acetal resinwith a hydroxyl content of 25 to 40 mol % (pattern (ii)).

In the pattern (i), specifically, the interlayer film has a monolayerstructure or a multilayer structure including at least two layers andincludes the first layer containing a thermoplastic resin, a firstplasticizer represented by the formula (1), and a second plasticizerthat is a diester compound. In the pattern (i), the interlayer film hasa monolayer structure and includes the first layer containing athermoplastic resin, a first plasticizer represented by the formula (1),and a second plasticizer that is a diester compound (pattern i-1), oralternatively, the interlayer film has a multilayer structure includingat least two layers and includes the first layer containing athermoplastic resin, a first plasticizer represented by the formula (1),and a second plasticizer that is a diester compound (pattern i-2). Inthe pattern (i-2), components contained in the second layer are notparticularly limited. The second layer preferably contains athermoplastic resin, more preferably a thermoplastic resin and aplasticizer, and still more preferably a polyvinyl acetal resin and aplasticizer.

In the formula (1), R1 and R2 each represent an organic group having atleast one ether bond, and n represents an integer of 2 to 8.

The above structure of the interlayer film for laminated glass accordingto the present invention allows increase in the sound insulation of alaminated glass including the interlayer film. In the case where theinterlayer film for laminated glass according to the present inventionhas a multilayer structure including at least two layers, the abovestructure of the multilayer interlayer film allows increase in the soundinsulation and penetration resistance of a laminated glass including theinterlayer film. Especially in the pattern (ii) “the interlayer film forlaminated glass according to the present invention has a multilayerstructure including at least two layers and includes the second layercontaining a plasticizer and a polyvinyl acetal resin with a hydroxylcontent of 25 to 40 mol %” and the pattern (i-2) “the interlayer filmhas a multilayer structure including at least two layers and includesthe first layer containing a thermoplastic resin, a first plasticizerrepresented by the formula (1), and a second plasticizer that is adiester compound”, the sound insulation and penetration resistance ofthe resulting laminated glass are efficiently increased.

The first plasticizer represented by the formula (1) increases the soundinsulation at comparatively low temperatures (around 0° C.). The secondplasticizer that is a diester compound increases the sound insulation atcomparatively high temperatures (around 20° C.). Combination use of thefirst plasticizer represented by the formula (1) and the secondplasticizer that is a diester compound allows increase in the soundinsulation of the laminated glass including the interlayer film forlaminated glass according to the present invention in a wide temperaturerange.

Use of only the first plasticizer represented by the formula (1) as theplasticizer tends to cause bleeding of the plasticizer. Especially inthe case where the interlayer film has a monolayer structure andincludes the first layer containing only the first plasticizerrepresented by the formula (1) as the plasticizer, the plasticizer tendsto bleed and the penetration resistance of the laminated glass tends tobe lowered. In contrast, use of the second plasticizer that is a diestercompound as well as the first plasticizer represented by the formula (1)in the first layer suppresses bleeding of the plasticizer. From thestandpoint of suppression of bleeding of the plasticizer, the firstlayer preferably contains the first plasticizer represented by theformula (1) and the second plasticizer that is a diester compound. Useof a laminate including the second layer stacked on the first layercontaining the first plasticizer suppresses the bleeding of theplasticizer and increases the penetration resistance of the laminatedglass. The second layer contributes to increase in the adhesiveness tothe components for laminated glass and increase in the penetrationresistance of the laminated glass. Especially, the second layercontaining the plasticizer and the polyvinyl acetal resin with ahydroxyl content of 25 to 40 mol % significantly contributes to increasein the penetration resistance of the laminated glass.

Hereinafter, the present invention will be described by means ofspecific embodiments and examples of the present invention, withreference to the drawings.

FIG. 1 is a partially notched cross-sectional view schematicallyillustrating an interlayer film for laminated glass according to a firstembodiment of the present invention.

An interlayer film 12 illustrated in FIG. 1 is a multilayer interlayerfilm having a multilayer structure including at least two layers, morespecifically having a multilayer structure including at least threelayers. More specifically, the interlayer film 12 has a multilayerstructure including three layers. The interlayer film 12 is used forforming a laminated glass. The interlayer film 12 is an interlayer filmfor laminated glass. The interlayer film 12 has a first layer 14(interlayer film), a second layer 13 (interlayer film) stacked on oneface 14 a (first face) of the first layer 14, and a second layer 15(interlayer film) stacked on the other face 14 b (second face) of thefirst layer 14.

In the first embodiment, the first layer 14 contains a thermoplasticresin and a first plasticizer represented by the formula (1). Thethermoplastic resin is preferably a polyvinyl acetal resin. In theinterlayer film 12, the first layer 14 is an intermediate layer. Thefirst layer is preferably an intermediate layer. Since the first layercontains a thermoplastic resin and the first plasticizer represented bythe formula (1), the sound insulation of the first layer is excellent.The first layer may be used as a sound insulation layer in the laminatedglass, for example.

The second layer 13 and the second layer 15 each contain a plasticizerand a polyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %.It is to be noted that in the case where the second layer 13 contains aplasticizer and a polyvinyl acetal resin with a hydroxyl content of 25to 40 mol %, the second layer 15 may not contain these components. Inthe interlayer film 12, the second layer 13 and the second layer 15 aresurface layers. The second layers are preferably surface layers. Thesecond layers may be used as protective layers in the laminated glass,for example.

The second layer 13 and the second layer 15 each contains a plasticizerand a polyvinyl acetal resin with a hydroxyl content of 25 to 40 mol %.In the case where the first layer 14 containing the second plasticizerthat is a diester compound in addition to the thermoplastic resin andthe first plasticizer represented by the formula (1), the componentscontained in the second layer 13 and the second layer 15 are notparticularly limited. In the case where the first layer 14 contains thesecond plasticizer that is a diester compound in addition to thethermoplastic resin and the first plasticizer represented by the formula(1), the second layer 13 and the second layer 15 each preferably containa thermoplastic resin, more preferably a thermoplastic resin and aplasticizer, and still more preferably a polyvinyl acetal resin and aplasticizer.

In the case of a multilayer interlayer film for laminated glass having amultilayer structure including at least two layers, the interlayer filmfor laminated glass according to the present invention includes thesecond layer stacked at least on one face of the first layer. Namely,the second layer may be formed only on one face of the first layer orthe second layers may be formed on one face (first face) and on theother face (second face). Both faces of the first layer may each haveone second layer stacked thereon. In the case where the second layersare stacked on both faces of the first layer, the second layers may bethe same as or different from each other. In the case where the secondlayer is stacked only on one face of the first layer, a layer differentfrom the second layer may be stacked on the other face of the firstlayer. For example, a layer containing heat insulating particles such asmetal oxide particles may be stacked on the other face of the firstlayer.

In the case of the multilayer interlayer film for laminated glass havinga multilayer structure including at least two layers, the interlayerfilm for laminated glass according to the present invention has at leastone first layer and at least one second layer, namely, both the firstlayer and the second layer. The interlayer film may optionally haveother layer(s) other than the first layer and the second layer. Forexample, use of a layer containing heat insulating particles such asmetal oxide particles increases the heat insulation.

FIG. 2 is a partially notched cross-sectional view schematicallyillustrating an interlayer film for laminated glass according to asecond embodiment of the present invention.

An interlayer film 2A illustrated in FIG. 2 has a first layer 2. Theinterlayer film 2A has a monolayer structure including only the firstlayer 2 and is a monolayer interlayer film. The interlayer film 2A isthe first layer 2. The interlayer film 2A is used for forming alaminated glass. The interlayer film 2A is an interlayer film forlaminated glass.

The interlayer film 2A and the first layer 2 contains the thermoplasticresin, the first plasticizer represented by the formula (1), and thesecond plasticizer that is a diester compound. The thermoplastic resinis preferably a polyvinyl acetal resin. Accordingly, the interlayer film2A having a monolayer structure contains the second plasticizer that isa diester compound, in addition to the thermoplastic resin and the firstplasticizer represented by the formula (1).

An interlayer film for laminated glass having a multilayer structurewith increased sound insulation tends to cause bubble formation andbubble growth. The present inventors have found out that, in aninterlayer film for laminated glass having a multilayer structure, theplasticizer migrates among layers to form a layer containing a largeramount of the plasticizer. For example, the plasticizer in the secondlayer may migrate to the first layer to increase the amount of theplasticizer in the first layer. Formation of a layer containing a largeamount of the plasticizer, namely, increase in the plasticizer contentof the first layer may cause easy bubble formation in the laminatedglass including the interlayer film for laminated glass. In addition,bubble formation is once generated, the generated bubbles may becomecore to cause bubble growth.

From the standpoint of suppression of bubble formation and bubblegrowth, the following composition is preferable. The amount of all theplasticizers is at least 50 parts by weight for 100 parts by weight ofthe polyvinyl acetal resin in the first layer, a hydroxyl content of thepolyvinyl acetal resin in the first layer is lower than a hydroxylcontent of the polyvinyl acetal resin in the second layer, a differencein the hydroxyl content is at most 9.2 mol % between the polyvinylacetal resin in the first layer and the polyvinyl acetal resin in thesecond layer (hereinafter, also referred to as content difference(1-2)), and in the case where the difference (content difference (1-2))in the hydroxyl content is more than 8.5 mol % and at most 9.2 mol %between the polyvinyl acetal resin in the first layer and the polyvinylacetal resin in the second layer, the polyvinyl acetal resin in thefirst layer has an acetylation degree of at most 8 mol %. The contentdifference (1-2) may be higher than 8.5 mol % and at most 9.2 mol %, andfurther may be at most 8.5 mol %.

The present inventors have made various studies to suppress bubbleformation and bubble growth, and have found that the bubble formationand the bubble growth in a laminated glass can be sufficientlysuppressed if the hydroxyl content of the polyvinyl acetal resin in eachof the first layer and the second layer is controlled as mentionedearlier. Since migration of the plasticizer can be inhibited, and alsobubble formation and bubble growth in the laminated glass can besufficiently suppressed, the amount of the plasticizer in each layer,especially the amount of the plasticizer in the first layer can beincreased. As a result, the sound insulation of the laminated glass canbe further increased.

It is to be noted that bubble formation is more likely to be caused inthe case where the amount of all the plasticizers for 100 parts byweight of the polyvinyl acetal resin in the first layer is larger thanthe amount of all the plasticizers for 100 parts by weight of thepolyvinyl acetal resin in the second layer. In addition, once bubbleformation is caused, the bubbles may become nuclei to cause bubblegrowth. To solve this problem, control of the hydroxyl content of thepolyvinyl acetal resin in each of the first layer and the second layeras mentioned earlier sufficiently suppresses bubble formation and bubblegrowth in the laminated glass.

In terms of further suppressing bubble formation and bubble growth inthe laminated glass, the minimum value of difference between thehydroxyl content of the polyvinyl acetal resin in the first layer andthe hydroxyl content of the polyvinyl acetal resin in the second layer(content difference (1-2)) is preferably 0.1 mol %, more preferably 1mol %, and still more preferably 2 mol %. The maximum value of thedifference is preferably 8.5 mol %, more preferably 7.8 mol %, stillmore preferably 7 mol %, and particularly preferably 5.6 mol %. Thedifference between the hydroxyl content of the polyvinyl acetal resin inthe first layer and the hydroxyl content of the polyvinyl acetal resinin the second layer (content difference (1-2)) is preferably at most 5mol %, more preferably at most 4.5 mol %, still more preferably at most4 mol %, and further preferably at most 3.5 mol % because bubbleformation and bubble growth in the laminated glass can be furthersuppressed.

The thermoplastic resin in the first layer preferably contains a highmolecular weight component having an absolute molecular weight of atleast 1 million (hereinafter, also referred to as high molecular weightcomponent X) or a high molecular weight component having apolystyrene-equivalent molecular weight (hereinafter, also referred toas high molecular weight y) of at least 1 million (hereinafter, alsoreferred to as high molecular weight component Y). The high molecularweight component X and the high molecular weight component Y each are athermoplastic resin. Preferably, the high molecular weight component Xaccounts for at least 7.4% of the thermoplastic resin in the firstlayer, or the high molecular weight component Y accounts for at least 9%of the thermoplastic resin in the first layer.

Bubble formation in the laminated glass is suppressed in the case wherethe thermoplastic resin in the first layer contains a specificproportion of the high molecular weight component X having an absolutemolecular weight of at least 1 million. Alternatively, bubble formationin the laminated glass is also suppressed in the case where thethermoplastic resin in the first layer contains a specific proportion ofthe high molecular weight component Y having a molecular weight y of atleast 1 million.

The proportion of the high molecular weight component X in thethermoplastic resin in the first layer is determined as a percentagevalue of the area of a region corresponding to the high molecular weightcomponent X occupying in the peak area of the thermoplastic resincomponent obtained in the measurement of the absolute molecular weight.The proportion of the high molecular weight component Y in thethermoplastic resin in the first layer is determined as a percentagevalue of the area of a region corresponding to the high molecular weightcomponent Y occupying in the peak area of the thermoplastic resincomponent obtained in the measurement of the molecular weight ofpolystyrene.

The second layer preferably has a composition different from that of thefirst layer. The polyvinyl acetal resin in the second layer may containthe high molecular weight component X having an absolute molecularweight of at least 1 million and the high molecular weight component Xmay account for at least 7.4% of the polyvinyl acetal resin in thesecond layer. Alternatively, the polyvinyl acetal resin in the secondlayer may contain the high molecular weight component Y having amolecular weight y of at least 1 million and the high molecular weightcomponent Y accounts for at least 9% of the polyvinyl acetal resin inthe second layer.

From the standpoint of further increase in the sound insulation of thelaminated glass and further suppression of bubble formation and bubblegrowth, the minimum value of proportion of the high molecular weightcomponent X having an absolute molecular weight of at least 1 million ispreferably 8%, more preferably 8.5%, still more preferably 9%,particularly preferably 9.5%, and most preferably 10%. From thestandpoint of still further increase in the sound insulation of thelaminated glass and further suppression of bubble formation and bubblegrowth, the proportion of the high molecular weight component X havingan absolute molecular weight of at least 1 million is preferably atleast 11%, more preferably at least 12%, still more preferably at least14%, and particularly preferably at least 16%. The upper limit of theproportion of the high molecular weight component X is not particularlylimited, and is preferably 40%, more preferably 30%, and still morepreferably 25%.

In the case where the thermoplastic resin in the first layer containsthe high molecular weight component Y having a molecular weight y of atleast 1 million, the minimum value of proportion of the high molecularweight component Y in the thermoplastic resin in the first layer ispreferably 10%, more preferably 11%, still more preferably 11.5%, andparticularly preferably 12%. From the standpoint of further increase inthe sound insulation of the laminated glass and further suppressingbubble formation and bubble growth, the proportion of the high molecularweight component Y is preferably at least 12.5%, more preferably atleast 13.5%, still more preferably at least 14%, particularly preferablyat least 15%, and most preferably at least 18%. The maximum value ofproportion of the high molecular weight component Y is not particularlylimited, and is preferably 40%, more preferably 30%, and still morepreferably 25%. The proportion of the high molecular weight component Yof at least the above lower limit further increases the sound insulationof the laminated glass and further suppresses bubble formation andbubble growth.

When a resin film A that contains 100 parts by weight of the polyvinylacetal resin in the first layer and 60 parts by weight oftriethyleneglycol di-2-ethylhexanoate (3GO) and has a glass transitiontemperature of Tg (° C.) is used for measurement of the viscoelasticity(testing method A), an elasticity G′(Tg+80) at (Tg+80)° C. and anelasticity G′(Tg+30) at (Tg+30)° C. preferably have a ratio(G′(Tg+80)/G′(Tg+30)) of at least 0.65.

Also, when the first layer is used as a resin film B and theviscoelasticity of the resin film B with a glass transition temperatureof Tg (° C.) is measured (testing method B), an elasticity G′(Tg+80) at(Tg+80)° C. and an elasticity G′(Tg+30) at (Tg+30)° C. preferably have aratio (G′(Tg+80)/G′ (Tg+30)) of at least 0.65.

In the testing method B, the first layer is used as the resin film B.Namely, the first layer itself is a resin film B.

The resin film B is the first layer. In the case where the resin film Bcontains the thermoplastic resin, the first plasticizer represented bythe formula (1), and another plasticizer different from the firstplasticizer, the resin film B contains the other plasticizer at theweight ratio in the first layer. In the testing method B, the elasticityG′(Tg+80) and the elasticity G′(Tg+30) are preferably measured aftermigration of the plasticizer in the interlayer film for laminated glass.In the testing method B, the elasticity G′(Tg+80) and the elasticityG′(Tg+30) are preferably measured after migration of the plasticizer inthe interlayer film for laminated glass during storage of the interlayerfilm for laminated glass at a humidity of 30% (±3%) and a temperature of23° C. for a month.

The present inventors have made various studies to suppress bubbleformation and bubble growth, and have found that the bubble formationand the bubble growth in a laminated glass can be sufficientlysuppressed if the ratio (G′(Tg+80)/G′(Tg+30)) determined by the testingmethod A or the testing method B is at least 0.65. Even if the totalamount of all the plasticizers in the first layer is large, bubbleformation and bubble growth in the laminated glass is sufficientlysuppressed. The sound insulation of the laminated glass can be thereforeincreased. Especially, bubble formation and bubble growth in thelaminated glass is further suppressed if the used interlayer film forlaminated glass in which the second layers are stacked on the both facesof the first layer is constituted to have a ratio (G′(Tg+80)/G′(Tg+30))of at least 0.65.

The ratio (G′(Tg+80)/G′(Tg+30)) is at least 0.65 and preferably at most1.0. The ratio (G′(Tg+80)/G′(Tg+30)) of at least 0.65 allows sufficientsuppression of bubble formation and bubble growth in the laminated glasseven if the laminated glass is stored under severe conditions or for along time. The ratio (G′(Tg+80)/G′(Tg+30)) of at least the above lowerlimit and at most the above upper limit allows more efficientsuppression of bubble formation and bubble growth in the laminated glasseven if the laminated glass is stored under severe conditions or for along time.

From the standpoint of sufficient increase in the sound insulation ofthe laminated glass, the total amount of all the plasticizers for 100parts by weight of the polyvinyl acetal resin in the first layer ispreferably at least 40 parts by weight. Even when the amount of theplasticizer in the first layer is large, bubble formation and bubblegrowth in the laminated glass can be suppressed by the first layerhaving a configuration that the ratio (G′(Tg+80)/G′(Tg+30)) is at least0.65.

The glass transition temperature Tg (° C.) represents a peak temperatureof the loss factor tan δ obtained from the results of theviscoelasticity measurement. From the standpoint of further suppressionof bubble formation and bubble growth in the laminated glass, the ratio(G′(Tg+80)/G′(Tg+30)) is more preferably at least 0.7 and at most 0.95,and more preferably at least 0.75 and at most 0.9. Especially, in thecase where the average degree of polymerization of a polyvinyl alcoholresin is utilized to control the ratio (G′(Tg+80)/G′(Tg+30)), sincebubble formation and bubble growth in the laminated glass aresufficiently suppressed and the sound insulation of the laminated glassis further increased, the ratio (G′(Tg+80)/G′(Tg+30)) is preferably atleast 0.65, more preferably at least 0.66, still more preferably atleast 0.67, and preferably at most 0.82 and still more preferably atmost 0.8. Moreover, when the ratio (G′(Tg+80)/G′(Tg+30)) is at most 0.82or at most 0.8, the interlayer film is easily formed.

Exemplary methods for setting the ratio (G′(Tg+80)/G′(Tg+30)) to atleast 0.65 by the testing method A or the testing method B include amethod of using a polyvinyl alcohol resin that has a comparatively highaverage degree of polymerization in synthesis of the polyvinyl acetalresin in the first layer, and a method of enhancing the interaction ofmolecules of the polyvinyl acetal resin in the first layer. Exemplarymethods of the method of enhancing the interaction of molecules of thepolyvinyl acetal resin in the first layer include physical crosslinkingand chemical crosslinking between molecules of the polyvinyl acetalresin. From the standpoint of easy formation of an interlayer film usingan extruder, particularly preferable methods are the method of using apolyvinyl alcohol resin that has a comparatively high average degree ofpolymerization in synthesis of the polyvinyl acetal resin in the firstlayer and physical crosslinking between molecules of the polyvinylacetal resin.

A description is given on one example of a relation between the lossfactor tan δ obtained in the viscoelasticity measurement and thetemperature and a relation between the elasticity G′ and the temperaturewith reference to FIG. 5.

The relation between the loss factor tan δ and the temperature is asillustrated in FIG. 5. The temperature at the peak P of the loss factortan δ is the glass transition temperature Tg.

The glass transition temperature Tg corresponding to the elasticity G′indicated by a dotted line A2 is the same temperature as the glasstransition temperature Tg corresponding to the elasticity G′ indicatedby a solid line A1 in FIG. 5. For example, a smaller change D in theelasticity G′(Tg+80) relative to the elasticity G′(Tg+30) allows moreefficient suppression of bubble formation and bubble growth in thelaminated glass. A change D1 in the elasticity G′ indicated by the solidline A1 is smaller than a change D2 in the elasticity G′ indicated bythe dotted line A2. In FIG. 5, therefore, bubble formation and bubblegrowth in the laminated glass is more efficiently suppressed in the caseof the elasticity G′ indicated by the solid line A1 which shows thecomparatively smaller change D1 than in the case of the elasticity G′indicated by the dotted line A2 which shows the comparatively largerchange D2.

The G′(Tg+30) is preferably at least 0.2 million Pa. The G′(Tg+30) ismore preferably at least 0.22 million Pa, still more preferably at least0.23 million Pa, and particularly preferably at least 0.24 million Pa.The G′(Tg+30) is preferably at most 10 million Pa, more preferably atmost 5 million Pa, still more preferably at most 1 million Pa,particularly preferably at most 0.5 million Pa, and most preferably 0.3million Pa. The G′(Tg+30) of at least above lower limit can moreefficiently suppress bubble formation and bubble growth in the laminatedglass.

The relation between the elasticity G′ and the temperature issignificantly affected by the kind of the polyvinyl acetal resin.Especially, the relation is greatly affected by the average degree ofpolymerization of the polyvinyl alcohol resin used for preparation ofthe polyvinyl acetal resin. The relation is not so much affected by thekind of the plasticizer. Also, the relation is not so much affected bythe amount of the plasticizer in normal plasticizer content. The ratio(G′(Tg+80)/G′(Tg+30)) in the case where a plasticizer other than 3GO,such as a monobasic organic ester, or the first plasticizer representedby the formula (1) is used as a plasticizer instead of 3GO, especiallythe ratio (G′(Tg+80)/G′(Tg+30)) in the case where the first plasticizerrepresented by the formula (1), triethyleneglycol di-2-ethylbutyrate(3GH), and triethyleneglycol di-n-heptanoate (3G7) are used is not sodifferent from the ratio (G′(Tg+80)/G′(Tg+30)) in the case where 3GO isused. When the total amount of all the plasticizers for 100 parts byweight of the polyvinyl acetal resin is 50 to 80 parts by weight, theratios (G′(Tg+80)/G′(Tg+30)) are not so much different from each other.The ratio (G′(Tg+80)/G′(Tg+30)) determined by using a resin filmcontaining 100 parts by weight of a polyvinyl acetal resin and 60 partsby weight of triethyleneglycol di-2-ethylhexanoate (3GO) as aplasticizer is not so much different from the ratio(G′(Tg+80)/G′(Tg+30)) determined by using the first layer itself. Theratios (G′(Tg+80)/G′(Tg+30)) obtained by the testing method A and thetesting method B are preferably both at least 0.65. More preferably, theratio (G′(Tg+80)/G′(Tg+30)) obtained by the testing method B is at least0.65.

For suppression of bubble formation in the interlayer film for laminatedglass, the polyvinyl acetal resin in the first layer is preferablyobtained by acetalization of a polyvinyl alcohol resin having an averagedegree of polymerization of more than 3000. In this case, the ratio(G′(Tg+80)/G′(Tg+30)) is not necessarily at least 0.65, but ispreferably at least 0.65. For further suppression of bubble formationand bubble growth in the laminated glass, the total amount of all theplasticizers is preferably at least 40 parts by weight for 100 parts byweight of the polyvinyl acetal resin obtained by acetalization of apolyvinyl alcohol resin having an average degree of polymerization ofmore than 3000 in the first layer. For further suppression of bubbleformation and bubble growth in the laminated glass, the polyvinyl acetalresin obtained by acetalization of a polyvinyl alcohol resin having anaverage degree of polymerization of more than 3000 preferably has ahydroxyl content of at most 30 mol %.

For further increase in the sound insulation of the laminated glass, thetotal amount of all the plasticizers for 100 parts by weight of thepolyvinyl acetal resin in the first layer is preferably at least 40parts by weight, more preferably at least 50 parts by weight, still morepreferably at least 55 parts by weight, and particularly preferably atleast 60 parts by weight. Accordingly, even if the plasticizer contentof the first layer is large, bubble formation and bubble growth in thelaminated glass is more efficiently suppressed by controlling thehydroxyl content of the polyvinyl acetal resin in each of the firstlayer and the second layer, by controlling the ratio of the highmolecular weight component X having an absolute molecular weight of atleast 1 million or the ratio of the high molecular weight component Yhaving a molecular weight y of at least 1 million, or by controlling theratio (G′(Tg+80)/G′(Tg+30)).

Hereinafter, detail descriptions are given on thermoplastic resins suchas a polyvinyl acetal resin and plasticizers such as the firstplasticizer and the second plasticizer contained in the interlayer filmfor laminated glass according to the present invention, and othercomponents used in the interlayer film for laminated glass.

(Thermoplastic Resin Contained in the First Layer)

The thermoplastic resin contained in the first layer is not particularlylimited, and a conventionally known thermoplastic resins may be used. Inthe case where the second layer contains a thermoplastic resin, thethermoplastic resin is not particularly limited, and a conventionallyknown thermoplastic resin may be used. Only one kind of thethermoplastic resin may be used, or two or more thermoplastic resins maybe used in combination.

Examples of the thermoplastic resin include polyvinyl acetal resins,ethylene-vinyl acetate copolymer resins, ethylene-acrylic copolymerresins, polyurethane resins, and polyvinyl alcohol resins.

The thermoplastic resin is preferably a polyvinyl acetal resin. Acombination use of a polyvinyl acetal resin and a specific firstplasticizer further increases the adhesiveness of the interlayer filmfor laminated glass according to the present invention to a componentfor laminated glass or the adhesiveness between layers. Thethermoplastic resin in the second layer is preferably a polyvinyl acetalresin. In this case, the adhesiveness between the second layer and thecomponent for laminated glass and the adhesiveness of the first layer tothe second layer are further increased. In addition, affinity betweenthe first layer and the second layer is increased, so that thetransparency of the interlayer film and the laminated glass is furtherincreased. Only one kind of the polyvinyl acetal resin may be used, ortwo or more polyvinyl acetal resins may be used in combination.

The polyvinyl acetal resin can be produced by acetalization of polyvinylalcohol with an aldehyde, for example. The polyvinyl alcohol can beproduced by saponification of polyvinyl acetate, for example. Thesaponification degree of the polyvinyl alcohol is commonly within arange of 70 to 99.9 mol %, preferably 75 to 99.8 mol %, and still morepreferably 80 to 99.8 mol %.

The polyvinyl alcohol preferably has an average degree of polymerizationof at least 200, more preferably at least 500, still more preferably atleast 1600, particularly preferably at least 2600, and most preferablyat least 2700. The average degree of polymerization is preferably atmost 5000, more preferably at most 4000, and still more preferably atmost 3500. The average degree of polymerization satisfying the lowerlimit further increases the penetration resistance of the laminatedglass. The average degree of polymerization satisfying the upper limitfacilitates formation of the interlayer film.

For inhibition of a sheet slippage of a laminated glass including theinterlayer film for laminated glass according to the present invention,the polyvinyl alcohol preferably has an average degree of polymerizationof at least 2600 and more preferably at least 2700. The sheet slippageindicates a phenomenon that one glass sheet slides to be dislocated fromthe other glass sheet due to its weight in the storage of the laminatedglass leaning on something in a high temperature environment.

For further increase in the penetration resistance of the laminatedglass, the polyvinyl alcohol especially preferably has an average degreeof polymerization of 2700 to 5000. In particular, for further increasein the penetration resistance of the laminated glass, the polyvinylacetal resin in the first layer is preferably obtained by acetalizationof polyvinyl alcohol having an average degree of polymerization of 2700to 5000.

For further suppression of bubble formation and bubble growth in thelaminated glass, the polyvinyl alcohol resin used for preparation of thepolyvinyl acetal resin in the first layer has the minimum average degreeof polymerization of preferably 3010, preferably 3050, preferably 3500,preferably 3600, preferably 4000, and preferably 4050. The maximumaverage degree of polymerization thereof is preferably 7000, preferably6000, preferably 5000, preferably 4900, and preferably 4500. Inparticular, for further suppression of bubble formation and bubblegrowth in the laminated glass, sufficient increase in the soundinsulation of the laminated glass, and easy formation of the interlayerfilm, the polyvinyl alcohol resin used for preparation of the polyvinylacetal resin in the first layer preferably has an average degree ofpolymerization of at least 3010, more preferably at least 3020,preferably at most 4000, more preferably less than 4000, still morepreferably at most 3800, particularly preferably at most 3600, and mostpreferably at most 3500.

The polyvinyl acetal resin in the second layer may be produced byacetalization of a polyvinyl alcohol resin. The polyvinyl alcohol resinused for preparation of the polyvinyl acetal resin in the second layerpreferably has the minimum average degree of polymerization of 200, morepreferably 500, still more preferably 1000, and particularly preferably1500. The maximum average degree of polymerization thereof is preferably4000, more preferably 3500, still more preferably 3000, and particularlypreferably 2500. The average degree of polymerization satisfying thepreferable lower limit further increases the penetration resistance ofthe laminated glass. The average degree of polymerization satisfying thepreferable upper limit facilitates formation of the interlayer film.

The polyvinyl alcohol resin used for preparation of the polyvinyl acetalresin in the first layer preferably has an average degree ofpolymerization higher than that of the polyvinyl alcohol resin used forpreparation of the polyvinyl acetal resin in the second layer. Thedifference is preferably at least 500, preferably at least 800, morepreferably at least 1000, still more preferably at least 1300, andparticularly preferably at least 1800.

The average degree of polymerization of the polyvinyl alcohol isdetermined by a method in accordance with JIS K 6726 “Testing methodsfor polyvinyl alcohol”.

The carbon number of the acetal group contained in the polyvinyl acetalresin is not particularly limited. The aldehyde used in preparation ofthe polyvinyl acetal resin is not particularly limited. The carbonnumber of the acetal group in the polyvinyl acetal resin is preferably 3or 4. The carbon number of at least 3 sufficiently lowers the glasstransition temperature of the interlayer film and further increases thesound insulation for solid born sounds at low temperatures.

The aldehyde is not particularly limited. Commonly, aldehydes having 1to 10 carbon atom(s) are suitably used. Examples of the aldehydes having1 to 10 carbon atom(s) include n-butylaldehyde, isobutylaldehyde,n-valeraldehyde, 2-ethylbutylaldehyde, n-hexylaldehyde, n-octylaldehyde,n-nonylaldehyde, n-decylaldehyde, formaldehyde, acetaldehyde, andbenzaldehyde. In particular, propionaldehyde, n-butylaldehyde,isobutylaldehyde, n-hexylaldehyde, or n-valeraldehyde is preferablyused. Moreover, propionaldehyde, n-butylaldehyde, or isobutylaldehyde ismore preferably used, and n-butylaldehyde is still more preferably used.Each of these aldehydes may be used alone, or two or more of them may beused in combination.

The carbon number of the acetal group in the polyvinyl acetal resin inthe second layer is preferably 3 or 4. The carbon number of at least 3sufficiently lowers the glass transition temperature of the interlayerfilm and further increases the sound insulation for solid born sounds atlow temperatures. The aldehyde used in acetalization is preferablypropionaldehyde, n-butylaldehyde, isobutylaldehyde, n-hexylaldehyde, orn-valeraldehyde. More preferably, the aldehyde is propionaldehyde,n-butylaldehyde, or isobutylaldehyde. Still more preferably, thealdehyde is n-butylaldehyde. Each of these aldehydes may be used alone,or two or more of them may be used in combination.

The polyvinyl acetal resin is preferably a polyvinyl butyral resin. Theinterlayer film for laminated glass according to the present inventionpreferably contains a polyvinyl butyral resin as the polyvinyl acetalresin in each of the first layer and the second layer. A polyvinylbutyral resin can be easily synthesized. Use of a polyvinyl butyralresin contributes to still more appropriate adhesiveness of theinterlayer film to the component for laminated glass. Further, the useleads to a further increase in the properties such as light resistanceand weather resistance.

The hydroxyl content (the amount of the hydroxyl group) of the polyvinylacetal resin in the first layer is at least 0 mol %, preferably at least10 mol %, more preferably at least 15 mol %, and still more preferablyat least 18 mol %. The hydroxyl content is preferably at most 40 mol %,more preferably at most 35 mol %, particularly preferably at most 25 mol%, and most preferably at most 24 mol %. If the hydroxyl contentsatisfies the lower limit, bleeding of the plasticizer is hardly causedand the moisture resistance of the interlayer is further increased. Ifthe hydroxyl content satisfies the preferable maximum amount, thelaminated glass may have further increased penetration resistance.Further, the interlayer film can have higher flexibility, and cantherefore show even higher handling properties. For further increase inthe sound insulation of the laminated glass in a high frequency area,the lower hydroxyl content of the polyvinyl acetal resin in the firstlayer is better. The hydroxyl content of the polyvinyl acetal resin inthe first layer may be 0 mol %.

Especially, the hydroxyl content of at most 25 mol % in the first layerallows further increase in the moisture resistance of the interlayerfilm and the laminated glass.

The hydroxyl content of the polyvinyl acetal resin in the second layeris preferably 25 to 40 mol %. The hydroxyl content within this rangeefficiently increases the penetration resistance of the interlayer filmand the laminated glass and improves the handling properties of theinterlayer film. The hydroxyl content of the polyvinyl acetal resin inthe second layer is more preferably at least 26 mol %, particularlypreferably at least 27 mol %, and most preferably at least 30 mol %. Thehydroxyl content is preferably at most 37 mol %, particularly preferablyat most 34 mol %, and most preferably at most 32 mol %.

For further increase in the sound insulation of the laminated glass, thehydroxyl content of the polyvinyl acetal resin in the first layer ispreferably lower than that of the polyvinyl acetal resin in the secondlayer. For further increase in the sound insulation of the laminatedglass, the hydroxyl content of the polyvinyl acetal resin in the firstlayer is preferably lower than that of the polyvinyl acetal resin in thesecond layer by at least 1 mol %, more preferably by at least 3 mol %,still more preferably at least 5 mol %, and particularly preferably atleast 7 mol %.

The hydroxyl content of the polyvinyl acetal resin is a mole fractionobtained by dividing the amount of ethylene groups to which hydroxylgroups are bonded by the total amount of ethylene groups in the mainchain. It is possible to obtain the amount of ethylene groups to whichhydroxyl groups are bonded, for example, by measuring the amount ofethylene groups to which hydroxyl groups of polyvinyl alcohol as a rawmaterial are bonded in accordance with JIS K6726 “Testing Methods forPolyvinyl Alcohol”.

The polyvinyl acetal resin in the first layer preferably has anacetylation degree (the amount of acetyl groups) of at least 0.1 mol %,more preferably at least 0.3 mol %, still more preferably at least 0.5mol %, and particularly preferably at least 15 mol %. The acetylationdegree is preferably at most 30 mol %, more preferably at most 25 mol %,and still more preferably at most 20 mol %. The acetylation degreesatisfying the above lower limit increases the affinity between thepolyvinyl acetal resin and the plasticizer. In addition, the glasstransition temperature of the polyvinyl acetal resin is sufficientlyincreased. The acetylation degree satisfying the above upper limitfurther increases the moisture resistance of the interlayer film and thelaminated glass.

The polyvinyl acetal resin in the second layer preferably has anacetylation degree of at least 0 mol % and preferably at least 0.5 mol%. The acetylation degree is preferably at most 10 mol % and morepreferably at most 3 mol %. The acetylation degree satisfying the aboveupper limit enhances the strength of the interlayer film and suppressesbleeding of the plasticizer.

The polyvinyl acetal resin in the second layer preferably has anacetylation degree of at most 3 mol %. The acetylation degree of at most3 mol % increases the affinity between the polyvinyl acetal resin andthe plasticizer. Accordingly, bleeding of the plasticizer is furthersuppressed.

The polyvinyl acetal resin in the second layer preferably has anacetalization degree (or butyralization degree) of 55 to 75 mol %. Theacetalization degree of within this range hardly causes bleeding of theplasticizer. The acetalization degree satisfying the above lower limitincreases the moisture resistance of the interlayer film and thelaminated glass. The acetalization degree is preferably at least 58 mol%, more preferably at least 60 mol %, and particularly preferably atleast 62 mol %. The acetalization degree is preferably at most 72 mol %,more preferably at most 69 mol %, and particularly preferably at most 66mol %.

The acetylation degree in the first layer is obtained as describedbelow. The amounts of ethylene groups to which acetal groups are bondedand to which hydroxyl groups are bonded are subtracted from the totalamount of ethylene groups in the main chain. The obtained value isdivided by the total amount of ethylene groups in the main chain. Theobtained mole fraction expressed as percent is the acetylation degree.The amount of ethylene groups to which acetal groups are bonded can bemeasured in accordance with JIS K6728 “Testing Methods for Polyvinylbutyral”.

The polyvinyl acetal resin in the first layer preferably has anacetalization degree (butyralization degree in the case of a polyvinylbutyral resin) of at least 60 mol % and more preferably at least 63 mol%. The acetalization degree is preferably at most 85 mol %, morepreferably at most 75 mol %, and still more preferably at most 70 mol %.The acetalization degree satisfying the above lower limit increases theaffinity between the polyvinyl acetal resin and the plasticizer. Theacetalization degree satisfying the above upper limit shortens thereaction time needed for production of the polyvinyl acetal resin.

The acetalization degree is a mole fraction expressed as percentobtained by dividing the amount of ethylene groups to which acetalgroups are bonded by the total amount of ethylene groups in the mainchain.

It is possible to obtain the acetalization degree by measuring theamount of acetyl groups and the amount of vinyl alcohol in accordancewith JIS K6728 “Testing methods for Polyvinyl butyral”, calculating themole fractions based on the measurement results, and subtracting themole fractions of the amount of acetyl groups and of the amount of vinylalcohol from 100 mol %.

When a polyvinyl butyral resin is used as the polyvinyl acetal resin, itis possible to obtain the acetalization degree (butiralyzation degree)and the amount of acetyl groups from the measurements in accordance withJIS K6728 “Testing methods for Polyvinyl butyral”.

For further increase in the moisture resistance and penetrationresistance of the interlayer film and the laminated glass, the acetalgroup of the polyvinyl acetal resin in the second layer particularlypreferably has 3 or 4 carbon atoms, an acetalization degree of 60 to 75mol %, and an acetylation degree of 0 to 10 mol %. The polyvinyl acetalresin having at least 3 carbon atoms in the second layer sufficientlylowers the glass transition temperature of the interlayer film andfurther increases the sound insulation for solid born sounds at lowtemperatures.

For easy control of migration of the plasticizer and further increase inthe sound insulation of the laminated glass, the polyvinyl acetal resin(1) in the first layer preferably has an acetylation degree exceeding 8mol % when the content difference (1-2) is at most 8.5 mol %.

For easy control of migration of the plasticizer and further increase inthe sound insulation of the laminated glass, the polyvinyl acetal resin(1) in the first layer preferably has an acetalization degree of atleast 68 mol % or a hydroxyl content of less than 31.5 mol % when thecontent difference (1-2) is exceeding 8.5 mol % and at most 9.2 mol % orthe content difference (1-2) is at most 9.2 mol %.

For further suppression of bubble formation and bubble growth in thelaminated glass and further increase in the sound insulation of thelaminated glass, the polyvinyl acetal resin (1) contained in the firstlayer is preferably a polyvinyl acetal resin having an acetylationdegree of less than 8 mol % (hereinafter, also referred to as “polyvinylacetal resin A”) or a polyvinyl acetal resin having an acetylationdegree of at least 8 mol % (hereinafter, also referred to as “polyvinylacetal resin B”).

The polyvinyl acetal resin A has an acetylation degree a of less than 8mol %, preferably at most 7.5 mol %, preferably at most 7 mol %,preferably at most 6 mol %, and preferably at most 5 mol %. Theacetylation degree a is preferably at least 0.1 mol %, preferably atleast 0.5 mol %, preferably at least 0.8 mol %, preferably at least 1mol %, preferably at least 2 mol %, preferably at least 3 mol %, andpreferably at least 4 mol %. The acetylation degree a satisfying theabove upper limit and lower limit further increases the affinity betweenthe polyvinyl acetal resin and the plasticizer and further increases thesound insulation of the laminated glass.

The polyvinyl acetal resin A preferably has the minimum acetalizationdegree a of 68 mol %, more preferably 70 mol %, still more preferably 71mol %, and particularly preferably 72 mol %. The maximum acetalizationdegree a is preferably 85 mol %, more preferably 83 mol %, still morepreferably 81 mol %, and particularly preferably 79 mol %. Theacetalization degree a satisfying the lower limit further increases thesound insulation of the laminated glass. The acetalization degree asatisfying the upper limit shortens the reaction time needed forproduction of the polyvinyl acetal resin A.

The polyvinyl acetal resin A preferably has a hydroxyl content a of atmost 30 mol %, preferably at most 27.5 mol %, preferably at most 27 mol%, preferably at most 26 mol %, preferably at most 25 mol %, preferablyat most 24 mol %, preferably at most 23 mol %. The hydroxyl content a ispreferably at least 16 mol %, preferably at least 18 mol %, preferablyat least 19 mol %, and preferably at least 20 mol %. The hydroxylcontent a satisfying the upper limit further increases the soundinsulation of the laminated glass. The hydroxyl content a satisfying thelower limit further increases the adhesiveness of the interlayer film.

The polyvinyl acetal resin A is preferably a polyvinyl butyral resin.

The polyvinyl acetal resin B preferably has an acetylation degree b ofat least 8 mol %, preferably at least 9 mol %, preferably at least 10mol %, preferably at least 11 mol %, and preferably at least 12 mol %.The acetylation degree b is preferably at most 30 mol %, preferably atmost 28 mol %, preferably at most 26 mol %, preferably at most 24 mol %,preferably at most t 20 mol %, and preferably at most 19.5 mol %. Theacetylation degree b satisfying the lower limit further increases thesound insulation of the laminated glass. The acetylation degree bsatisfying the upper limit shortens the reaction time needed forproduction of the polyvinyl acetal resin B. In particular, for furthershortening of the reaction time needed for production of the polyvinylacetal resin B, the polyvinyl acetal resin B preferably has anacetylation degree b of less than 20 mol %.

The polyvinyl acetal resin B preferably has the minimum acetalizationdegree b of 50 mol %, more preferably 52.5 mol %, still more preferably54 mol %, and particularly preferably 60 mol %. The maximumacetalization degree b is preferably 80 mol %, more preferably 77 mol %,still more preferably 74 mol %, and particularly preferably 71 mol %.The acetalization degree b satisfying the lower limit further increasesthe sound insulation of the laminated glass. The acetalization degree bsatisfying the upper limit shortens the reaction time needed forproduction of the polyvinyl acetal resin B.

The polyvinyl acetal resin B preferably has a hydroxyl content b of atmost 30 mol %, preferably at most 27.5 mol %, preferably at most 27 mol%, preferably at most 26 mol %, and preferably at most 25 mol %. Thehydroxyl content b is preferably at least 18 mol %, preferably at least20 mol %, preferably at least 22 mol %, and preferably at least 23 mol%. The hydroxyl content b satisfying the upper limit further increasesthe sound insulation of the laminated glass. The hydroxyl content bsatisfying the lower limit further increases the adhesiveness of theinterlayer film.

The polyvinyl acetal resin B is preferably a polyvinyl butyral resin.

The polyvinyl acetal resin A and the polyvinyl acetal resin B are eachpreferably obtained by acetalization of a polyvinyl alcohol resin havingan average degree of polymerization exceeding 3000 with an aldehyde. Thealdehyde preferably has 1 to 10 carbon atom(s), and more preferably 4 or5 carbon atoms. The polyvinyl alcohol resin preferably has the minimumaverage degree of polymerization of 3010, preferably 3050, preferably3500, preferably 3600, preferably 4000, and preferably 4050. The maximumaverage degree of polymerization is preferably 7000, preferably 6000,preferably 5000, preferably 4900, and preferably 4500. The polyvinylacetal resin A and the polyvinyl acetal resin B in the first layer areeach particularly preferably obtained by acetalization of a polyvinylalcohol resin having an average degree of polymerization of exceeding3000 and less than 4000. Especially, for further suppression of bubbleformation and bubble growth in the laminated glass, sufficient increasein the sound insulation of the laminated glass, and easy formation ofthe interlayer film, the polyvinyl alcohol resin used in the productionof the polyvinyl acetal resin A and the polyvinyl acetal resin B in thefirst layer preferably has an average degree of polymerization of atleast 3010, more preferably at least 3020, preferably at most 4000, morepreferably less than 4000, still more preferably at most 3800,particularly preferably at most 3600, and most preferably at most 3500.

The thermoplastic resin preferably has the minimum weight averagemolecular weight of 0.1 million and more preferably 0.3 million. Themaximum weight average molecular weight is preferably 10 million andmore preferably 5 million. The weight average molecular weight of thethermoplastic resin below the preferable lower limit may lower thestrength of the interlayer film. The weight average molecular weight ofthe thermoplastic resin above the preferable upper limit may too muchenhance the strength of the interlayer film. The weight averagemolecular weight is the polystyrene-equivalent molecular weightdetermined by gel permeation chromatography (GPC).

The weight average molecular weight is the polystyrene-equivalent weightaverage molecular weight determined by gel permeation chromatography(GPC). For example, the polystyrene-equivalent weight average molecularweight is determined by gel permeation chromatography using polystyreneof known molecular mass as a standard sample. As a polystyrene standardsample (“Shodex Standard SM-105”, “Shodex Standard SH-75”produced bySHOWA DENKO K.K.), 14 samples are used which have a weight averagemolecular weight of 580, 1260, 2960, 5000, 10100, 21000, 28500, 76600,196000, 630000, 1130000, 2190000, 3150000, and 3900000. Theapproximation straight line obtained by plotting the molecular weightrelative to the elution time indicated by the peak top of the standardsample peak is used as a calibration curve. A surface layer (the secondlayer) and an intermediate layer (the first layer) are removed from amultilayer interlayer film having been left for a month in a steadytemperature and humidity room (humidity of 30%(±3%), temperature 23°C.). The removed first layer (intermediate layer) is dissolved intetrahydrofuran (THF) to provide a 0.1 wt % solution. The weight averagemolecular weight of the resulting solution is measured by analysis usinga GPC device. The weight average molecular weight is analyzed by using aGPC device (“RI: L2490, Autosampler: L-2200, Pump: L-2130, Column oven:L-2350, Column: series of GL-A120-S and GL-A100MX-S” produced by HitachiHigh-Technologies Corporation) connected with a light scatteringdetector for GPC (“Model 1270 (RALS+VISCO)” produced by VISCOTEK).

(Production method of a thermoplastic resin containing the highmolecular weight component X having an absolute molecular weight of atleast 1 million or the high molecular weight component Y having amolecular weight y of at least 1 million)

A description is given on a specific production method of a polyvinylacetal resin containing the high molecular weight component X having anabsolute molecular weight of at least 1 million or the high molecularweight component Y having a molecular weight y of at least 1 million asone example of the thermoplastic resin containing the high molecularweight component X having an absolute molecular weight of at least 1million or the high molecular weight component Y having a molecularweight y of at least 1 million in an amount satisfying the above lowerlimit.

First, a polyvinyl alcohol is prepared. The polyvinyl alcohol isobtainable, for example, by saponification of polyvinyl acetate. Thepolyvinyl alcohol has a saponification degree of commonly 70 to 99 mol%, preferably 75 to 99.8 mol %, and more preferably 80 to 99.8 mol %.

The minimum polymerization degree of the polyvinyl alcohol is preferably200, more preferably 500, still more preferably 1000, and particularlypreferably 1500. The maximum polymerization degree thereof is preferably3000, more preferable 2900, still more preferably 2800, and particularlypreferably 2700. If the polymerization degree is too low, thepenetration resistance of the laminated glass tends to be lowered. Incontrast, if the polymerization degree is too high, the interlayer filmmay be hardly formed.

Next, the polyvinyl alcohol is reacted with an aldehyde by using acatalyst to be acetalized. In this reaction, a solution containing thepolyvinyl alcohol may be used. Examples of the solvent used in thesolution containing the polyvinyl alcohol include water.

The production method of the polyvinyl acetal resin contained in thefirst layer preferably includes the step of reacting a polyvinyl alcoholwith an aldehyde with use of a catalyst for acetalization of thepolyvinyl alcohol.

The production method of the first layer preferably includes the stepsof reacting a polyvinyl alcohol with an aldehyde by using a catalyst sothat the polyvinyl alcohol is acetalized to give a polyvinyl acetalresin, and forming the first layer using a mixture containing theresulting polyvinyl acetal resin and a plasticizer. In the step offormation of the first layer or after formation of the first layer, asecond layer is stacked on the first layer so that a multilayerinterlayer film is obtained. Alternatively, co-extrusion of the firstlayer and the second layer may be employed to produce a multilayerinterlayer film.

The aldehyde is not particularly limited. Commonly, aldehydes having 1to 10 carbon atom(s) are favorably used. Examples of the aldehydeshaving 1 to 10 carbon atom(s) include propoionaldehyde, n-butylaldehyde,isobutylaldehyde, n-valeraldehyde, 2-ethylbutylaldehyde,n-hexylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde,formaldehyde, acetaldehyde, and benzaldehyde. In particular,n-butylaldehyde, n-hexylaldehyde, or n-valeraldehyde is preferable.Moreover, n-butylaldehyde is more preferable. Each of these aldehydesmay be used alone, or two or more of these may be used in combination.

For easy production of the polyvinyl acetal resin containing a specificamount of the high molecular weight component X having an absolutemolecular weight of at least 1 million or the high molecular weightcomponent Y having a molecular weight y of at least 1 million, a methodof adding a crosslinking agent such as a dialdehyde before or in themiddle of the acetalization reaction using an aldehyde for crosslinkingthe main chain of polyvinyl alcohols adjacent to each other may beemployed. For other examples, a method of promoting the acetalizationreaction between molecules by addition of an excessive amount ofaldehyde and a method of adding a polyvinyl alcohol having a highpolymerization degree may be indicated. Each of these methods may beused alone, or two or more methods may be employed in combination.

The catalyst is preferably an acid catalyst. Examples of the acidcatalyst include nitric acid, hydrochloric acid, sulfuric acid,phosphoric acid, and paratoluene sulfonic acid.

The polystyrene-equivalent molecular weight indicates a molecular weightindicated as the molecular weight of polystyrene determined by gelpermeation chromatography (GPC). The proportion (%) of the highmolecular weight component Y having the molecular weight y of at least 1million in the polyvinyl acetal resin is determined as a percentagevalue of the area of a region corresponding to the molecular weight y ofat least 1 million occupying in the peak area detected by a refractiveindex detector in the measurement of the polystyrene-equivalentmolecular weight of the polyvinyl acetal resin by GPC.

The polystyrene-equivalent molecular weight is determined as mentionedbelow, for example.

The polystyrene-equivalent molecular weight is determined by gelpermeation chromatography using polystyrene of known molecular mass as astandard sample. As a polystyrene standard sample (“Shodex StandardSM-105”, “Shodex Standard SH-75”produced by SHOWA DENKO K.K.), 14samples are used which have a weight average molecular weight of 580,1260, 2960, 5000, 10100, 21000, 28500, 76600, 196000, 630000, 1130000,2190000, 3150000, and 3900000.

The approximation straight line obtained by plotting the weight averagemolecular weight relative to the elution time indicated by the peak topof the standard sample peak is used as a calibration curve. For example,in the case where the proportion (%) of the high molecular weightcomponent Y having the molecular weight y of at least 1 millionoccupying in the polyvinyl acetal resin in an intermediate layer of amultilayer interlayer film in which a surface layer, an intermediatelayer, and a surface layer are stacked in the stated order, the surfacelayer and the intermediate layer are removed from the multilayerinterlayer film having been left for a month in a steady temperature andhumidity room (humidity of 30%(±3%), temperature of 23° C.). The removedintermediate layer is dissolved in tetrahydrofuran (THF) to provide a0.1 wt % solution. The peak area of the polyvinyl acetal resin in theintermediate layer is measured by analysis of the resulting solutionusing a GPC device. Next, the area is calculated which corresponds tothe region where the polystyrene-equivalent molecular weight of thepolyvinyl acetal resin in the intermediate layer is at least 1 million,based on the elution time of the polyvinyl acetal resin in theintermediate layer and the calibration curve. The area of the regionwhere the polystyrene-equivalent molecular weight of the polyvinylacetal resin in the intermediate layer is at least 1 million is dividedby the peak area of the polyvinyl acetal resin in the intermediatelayer, and the obtained value is expressed as a percentage value. Inthis manner, the proportion (%) of the high molecular weight component Yoccupying in the polyvinyl acetal resin is calculated. For example, thepolystyrene-equivalent molecular weight is determined by using a GelPermeation Chromatography (GPC) device (“RI: L2490, Autosampler: L-2200,Pump: L-2130, Column oven: L-2350, Column: series of GL-A120-S andGL-A100MX-S” produced by Hitachi High-Technologies Corporation).

(Plasticizer Contained in the First Layer and the Second Layer)

The first plasticizer contains the first plasticizer represented by theformula (1). The first layer preferably contains the second plasticizerthat is a diester compound. The second layer preferably contains aplasticizer. The second layer may contain the first plasticizerrepresented by the formula (1). The second layer preferably contains thesecond plasticizer that is a diester compound. With regard to the firstplasticizer and the second plasticizer, respectively, only one kind of aplasticizer may be used or two or more kinds of plasticizers may be usedin combination.

In the formula (1), R1 and R2 each represent an organic group having atleast one ether bond, and n represents an integer of 2 to 8.

From the standpoint of further increase in the sound insulation of theinterlayer film and the laminated glass, R1 and R2 in the formula (1)each preferably have at least one ether bond structural unit representedby the formula (11) or (12).

From the standpoint of further increase in the sound insulation of theinterlayer film and the laminated glass, R1 is preferably a grouprepresented by the formula (21) and R2 is preferably a group representedby the formula (26) in the formula (1).

In the formula (21), R21 represents an alkyl group having 1 to 10 carbonatom(s), R22 represents an alkylene group having 1 to 10 carbon atom(s),and m1 represents an integer of 1 to 5. In the formula (21), the minimumcarbon number of R21 is preferably 2, more preferably 3, and still morepreferably 4. The maximum carbon number thereof is preferably 9, morepreferably 8, still more preferably 7, and particularly preferably 6. Inthe formula (21), the minimum carbon number of R22 is preferably 2, morepreferably 3, and still more preferably 4. The maximum carbon numberthereof is preferably 9, more preferably 8, still more preferably 7, andparticularly preferably 6.

In the formula (26), R26 represents an alkyl group having 1 to 10 carbonatom(s), R27 represents an alkylene group having 1 to 10 carbon atom(s),and m2 represents an integer of 1 to 5. In the formula (26), the minimumcarbon number of R27 is preferably 2, more preferably 3 and still morepreferably 4. The maximum carbon number thereof is preferably 9, morepreferably 8, still more preferably 7, and particularly preferably 6. Inthe formula (26), the minimum carbon number of R27 is preferably 2, morepreferably 3, and still more preferably 4. The maximum carbon numberthereof is preferably 9, more preferably 8, still more preferably 7, andparticularly preferably 6.

Namely, the first plasticizer represented by the formula (1) ispreferably a first plasticizer represented by the formula (1A).

In the formula (1A), R21 and R26 each represent an alkyl group having 1to 10 carbon atom(s), R22 and R27 each represent an alkylene grouphaving 1 to 10 carbon atom(s), m1 and m2 each represent an integer of 1to 5, and n represents an integer of 2 to 8.

Specific examples of R1 and R2 include a 2-butoxyethyl group, a2-(2-butoxyethoxy)ethyl group, and a 2-[2-(2-butoxyethoxy)ethoxy]ethylgroup. It is to be noted that R1 and R2 each may be a group other thanthese examples.

The second layer preferably contains a plasticizer. The plasticizercontained in the second layer is not particularly limited. Aconventionally known plasticizer may be used as the plasticizer. In thesecond layer, only one kind of a plasticizer may be used or two or moreplasticizers may be used in combination.

Examples of the plasticizer contained in the second layer includeorganic ester plasticizers such as a monobasic organic acid ester and apolybasic organic acid ester, and phosphate plasticizers such as anorganic phosphate plasticizer and an organic phosphite acid plasticizer.Among these, an organic ester plasticizer is preferable. The plasticizeris preferably a liquid plasticizer.

Examples of the monobasic organic acid ester include, but notparticularly limited to, a glycol ester obtained through the reaction ofglycol and a monobasic organic acid, and an ester of a monobasic organicacid and one of triethylene glycol and tripropylene glycol. Examples ofthe glycol include triethylene glycol, tetraethylene glycol, andtripropylene glycol. Examples of the monobasic organic acid includebutyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid,heptylic acid, n-octyl acid, 2-ethylhexyl acid, n-nonylic acid, anddecylic acid.

Examples of the monobasic organic acid ester include, but notparticularly limited to, a glycol ester obtained through the reaction ofglycol and a monobasic organic acid, and an ester of a monobasic organicacid and one of triethylene glycol and tripropylene glycol. Examples ofthe glycol include triethylene glycol, tetraethylene glycol, andtripropylene glycol. Examples of the monobasic organic acid includebutyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid,heptylic acid, n-octyl acid, 2-ethylhexyl acid, n-nonylic acid, anddecylic acid.

Examples of the polybasic organic acid ester include, but notparticularly limited to, ester compounds of a polybasic organic acid anda C4 to C8 linear- or branched alcohol. Examples of the polybasicorganic acid include adipic acid, sebacic acid, and azelaic acid.

From the standpoint of further increase in the moisture resistance andthe penetration resistance of the interlayer film and the laminatedglass, the first layer preferably further contains the secondplasticizer that is a diester compound, in addition to the firstplasticizer represented by the formula (1).

From the standpoint of further increase in the moisture resistance andthe penetration resistance of the interlayer film and the laminatedglass, the plasticizer contained in the second layer is preferably thesecond plasticizer that is a diester compound. In the case where boththe first layer and the second layer contain the second plasticizersthat are diester compounds, the second plasticizers in the first layerand the second layer may be the same as or different from each other.

A conventionally known diester compound used in the interlayer film forlaminated glass may be used as the second plasticizer that is a diestercompound. The second plasticizer that is a diester compound ispreferably a second plasticizer represented by the formula (51). Thefirst layer preferably contains the second plasticizer represented bythe formula (51). The second layer preferably contains the secondplasticizer represented by the formula (51).

In the formula (51), R51 and R52 each represent an organic group having5 to 10 carbon atoms, R53 represents an ethylene group, isopropylenegroup or n-propylene group, and p represents an integer of 3 to 10.

Specific examples of the second plasticizer include triethyleneglycoldi-2-ethylbutylate (3GH), triethyleneglycol di-2-ethylhexanoate (3GO),triethyleneglycol di-n-heptanoate (3G7), triethyleneglycol dicaprylate,triethyleneglycol di-n-octanoate, tetraethyleneglycoldi-2-ethylbutyrate, tetraethyleneglycol di-n-heptanoate,tetraethyleneglycol di-2-ethylhexanoate, pentaethyleneglycoldi-2-ethylhexanoate, octaethyleneglycol di-2-ethylhexanoate,nonaethyleneglycol di-2-ethylhexanoate, decaethyleneglycoldi-2-ethylhexanoate, tetraethyleneglycol di-n-heptanoate, andtetraethyleneglycol di-n-octanoate.

From the standpoint of further increase in the penetration resistance ofthe interlayer film and the laminated glass, the second plasticizer ispreferably one selected from the group consisting of triethylene glycoldi-2-ethylbutyrate (3GH), triethylene glycol di-2-ethylhexanoate (3GO)and triethylene glycol di-n-heptanoate (3G7), and more preferablytriethylene glycol di-2-ethylhexanoate. Use of these preferableplasticizers can further increase the sound insulation of the laminatedglass. In addition, the moisture resistance and the penetrationresistance of the interlayer film and the laminated glass are alsoincreased.

In the first layer, the amount of the first plasticizer is preferablywithin 5 to 60 parts by weight. The amount of the first plasticizer for100 parts by weight of the thermoplastic resin is more preferably atleast 10 parts by weight and still more preferably at least 15 parts byweight. The amount of the first plasticizer is more preferably at most55 parts by weight and still more preferably at most 50 parts by weight.The amount of the first plasticizer which satisfies the above lowerlimit further increases the sound insulation of the interlayer film andthe laminated glass. The amount of the first plasticizer which satisfiesthe above upper limit hardly causes bleeding of the plasticizer andfurther increases the moisture resistance and the penetration resistanceof the interlayer film and the laminated glass.

In the case where the first layer contains the first plasticizer and thesecond plasticizer, the total amount of the first plasticizer and thesecond plasticizer for 100 parts by weight of the thermoplastic resin ispreferably within 50 to 80 parts by weight in the first layer. The totalamount of the first plasticizer and the second plasticizer for 100 partsby weight of the thermoplastic resin is preferably at least 55 parts byweight and more preferably at least 60 parts by weight. The total amountof the first plasticizer and the second plasticizer is preferably atmost 75 parts by weight and more preferably at most 70 parts by weight.The total amount of the first plasticizer and the second plasticizersatisfying the above lower limit further increases the sound insulationof the interlayer film and the laminated glass. The total amount of thefirst plasticizer and the second plasticizer satisfying the above upperlimit hardly causes bleeding of the plasticizer and further increasesthe moisture resistance and the penetration resistance of the interlayerfilm and the laminated glass.

In the case where the first layer contains the first plasticizer and thesecond plasticizer, the first layer preferably contains the firstplasticizer and the second plasticizer at a weight ratio (firstplasticizer:second plasticizer) of 0.1:9.9 to 9.9:0.1, more preferably1:9 to 8.5:1.5, particularly preferably 1:9 to 7:3, and most preferably3:7 to 6:4. A comparatively larger amount of the first plasticizer and acomparatively smaller amount of the second plasticizer further increasethe sound insulation of the interlayer film and the laminated glass. Acomparatively smaller amount of the first plasticizer and acomparatively larger amount of the second plasticizer further increasesthe moisture resistance and the penetration resistance of the interlayerfilm and the laminate glass.

In the second layer, the amount of the plasticizer (the amount of thesecond plasticizer in the case where the plasticizer is the secondplasticizer that is a diester compound) is preferably within 20 to 60parts by weight for 100 parts by weight of the thermoplastic resin. Theamount of the plasticizer is more preferably at least 25 parts by weightand still more preferably 30 parts by weight for 100 parts by weight ofthe thermoplastic resin. The amount of the plasticizer is morepreferably at most 50 parts by weight and still more preferably at most45 parts by weight for 100 parts by weight of the thermoplastic resin.The amount of the plasticizer which satisfies the above lower limitfurther increases the penetration resistance of the interlayer film andthe laminated glass. The amount of the plasticizer which satisfies theabove upper limit hardly causes bleeding of the plasticizer and furtherincreases the transparency of the interlayer film and the laminatedglass.

(Other Components)

The first layer and the second layer each may optionally containadditives such as an ultraviolet absorbent, an antioxidant, a lightstabilizer, a flame retardant, an antistatic agent, a pigment, a dye, anadhesion regulator, a moisture resistant agent, a fluorescent bleach,and an infrared absorbent. Each of these additives may be used alone, ortwo or more additives may be used in combination.

(Interlayer Film for Laminated Glass)

The interlayer film for laminated glass and the first layer according tothe present invention each exert excellent sound insulation so as to beused as the sound insulation layer in the laminated glass.

A temperature T1 indicating the maximum value of tan δ of the firstlayer at a frequency of 1 Hz is preferably within −30° C. to 0° C. Inthis case, the sound insulation of the interlayer film and the laminatedglass at low temperatures is further increased. The temperature T1indicating the maximum value of tan δ means the temperature indicatingthe maximum value of the obtained loss factor.

A temperature T2 indicating the maximum value of tan δ of the secondlayer at a frequency of 1 Hz is preferably higher than the temperatureT1 and more preferably within 0° C. to 40° C. The temperature T2 higherthan the temperature T1 further increases the sound insulation for solidborn sound not only at low temperatures but also in a 0° C. to 40° C.environment. Also, the temperature T2 within 0° C. to 40° C. increasesthe sound insulation for solid born sound in an ordinary temperaturerange. The ordinary temperature range means 5° C. to 35° C. Thetemperature T2 is more preferably higher than 0° C., still morepreferably at least 3° C., and particularly preferably at most 39° C.

In the case of a multilayer interlayer film for laminated glass having amultilayer structure including at least 2 layers, the first layerpreferably has a thickness of 0.02 to 1.8 mm. The thickness is morepreferably at least 0.05 mm and at most 0.5 mm. Such a favorablethickness does not make the multilayer interlayer film too thick andfurther increases the sound insulation of the multilayer interlayer filmand the laminated glass.

In the case of a multilayer interlayer film for laminated glass having amultilayer structure including at least 2 layers, the second layerpreferably has a thickness of 0.1 to 1 mm. The thickness is morepreferably at least 0.2 mm and at most 0.5 mm. The second layer having athickness satisfying the above lower and upper limits does not make themultilayer interlayer film too thick and further increases the soundinsulation of the multilayer interlayer film and the laminated glass. Inaddition, bleeding of the plasticizer is suppressed.

In the case of a monolayer interlayer film for laminated glass having amonolayer structure, the interlayer film for laminated glass accordingto the present invention preferably has a thickness (thickness of thefirst layer) of 0.1 to 3 mm. The thickness (thickness of the firstlayer) of the interlayer film is more preferably at least 0.25 mm and atmost 1.5 mm. The thickness of the interlayer film satisfying the abovelower limit sufficiently increases the penetration resistance of theinterlayer film and the laminated glass. The thickness of the interlayerfilm satisfying the above upper limit further increases the transparencyof the interlayer film.

In the case where the interlayer film has a multilayer structureincluding at least 2 layers, a smaller ratio of the thickness of thefirst layer to the thickness of the interlayer film ((thickness of thefirst layer)/(thickness of the interlayer film)) and a larger totalamount of all the plasticizers contained in the first layer tend toallow bubble formation and bubble growth in the laminated glass.Especially, the ratio in the interlayer film is preferably at least 0.05and at most 0.35. In this case, even with a large total amount of allthe plasticizers for 100 parts by weight of the polyvinyl acetal resinin the first layer, bubble formation and bubble growth in the laminatedglass are sufficiently suppressed and the sound insulation of thelaminated glass is further increased. The ratio ((thickness of the firstlayer)/(thickness of the interlayer film)) is preferably at least 0.06,more preferably at least 0.07, still more preferably at least 0.08, andparticularly preferably at least 0.1. The ratio is preferably at most0.3, more preferably at most 0.25, still more preferably at most 0.2,and particularly preferably 0.15.

A method for producing the interlayer film for laminated glass accordingto the present invention is not particularly limited and aconventionally known method may be employed. For example, thethermoplastic resin, plasticizers such as the first plasticizer and thesecond plasticizer, and, optionally, other additives may be mixed andkneaded. Then an interlayer film may be formed using the kneadedproduct. Extrusion molding is preferably employed as it is suitable forcontinuous production.

Examples of the kneading method include, but not particularly limitedto, a method using an extruder, plastograph, kneader, Banburymixer,calender roll, or the like. In particular, an extruder is preferablyused and a twin screw extruder is more preferably used because it issuitable for continuous production.

In the case where one second layer is stacked on each face of the firstlayer, both the second layers preferably contain the same polyvinylacetal resins, more preferably the same polyvinyl acetal resins and thesame plasticizers because the production efficiency of the interlayerfilm is enhanced. Moreover, both the second layers are still morepreferably formed of the same resin compositions.

(Laminated Glass)

FIG. 3 is a cross-sectional view illustrating an exemplary laminatedglass using an interlayer film for laminated glass 12 according to oneembodiment of the present invention.

A laminated glass 11 illustrated in FIG. 3 has an interlayer film 12 inwhich a second layer 13, a first layer 14, and a second layer 15 arestacked in the stated order, a first component for laminated glass 21and a second component for laminated glass 22. The interlayer film 12 issandwiched between the first component for laminated glass 21 and thesecond component for laminated glass 22. The first component forlaminated glass 21 is stacked on an outer face 13 a of the second layer13. The second component for laminated glass 22 is stacked on an outerface 15 a of the second layer 15.

FIG. 4 is a cross-sectional view illustrating one example of a laminatedglass including an interlayer film 2A for laminated glass according to asecond embodiment of the present invention.

A laminated glass 1 in FIG. 4 is provided with the interlayer film 2A(first layer 2), the first component for laminated glass 21 and thesecond component for laminated glass 22. The interlayer film 2A is amonolayer interlayer film and is the first layer 2. The interlayer film2A is sandwiched between the first component for laminated glass 21 andthe second component for laminated glass 22. The first component forlaminated glass 21 is stacked on one face 2 a of the interlayer film 2A.The second component for laminated glass 22 is stacked on the other face2 b of the interlayer film 2.

Accordingly, the laminated glass according to the present invention hasa first component for laminated glass, a second component for laminatedglass, and an interlayer film sandwiched between the first component forlaminated glass and the second component for laminated glass. Theinterlayer film used here is the interlayer film for laminated glass ofthe present invention.

Examples of the first component for laminated glass 21 and the secondcomponent for laminated glass 22 include glass sheets and PET(polyethylene terephthalate) films. The laminated glass 11 encompassesnot only a laminated glass having an interlayer film sandwiched betweentwo glass sheets but also a laminated glass having an interlayer filmsandwiched between a glass sheet and a PET film. The laminated glass 11is a laminated product provided with glass sheet (s) preferablyincluding at least one glass sheet.

Examples of the glass sheet include inorganic glass and organic glass.Examples of the inorganic glass include float plate glass, heatabsorbing plate glass, heat reflecting glass, polished plate glass,molded plate glass, wire plate glass, lined plate glass, and greenglass. The organic glass is a synthetic resin glass substituted forinorganic glass. Examples of the organic glass include polycarbonateplates and poly(meth)acrylic resin plates. Examples of thepoly(meth)acrylic resin plate include polymethyl(meth)acrylate plates.

The thickness of each of the first component for laminated glass 21 andthe second component for laminated glass 22 is preferably 1 to 5 mm. Inthe case where the first component for laminated glass 21 and the secondcomponent for laminated glass 22 are glass sheets, the thickness thereofis also preferably 1 to 5 mm. If the first component for laminated glass21 or the second component for laminated glass 22 is PET film, thethickness thereof is preferably 0.03 to 0.5 mm.

The method of producing the laminated glass 1 and the laminated glass 11are not particularly limited. For example, the interlayer film 2A or themultilayer interlayer film 12 is sandwiched between the first componentfor laminated glass 21 and the second component for laminated glass 22.The air remaining between the interlayer film 2A or the multilayerinterlayer film 12 and the first component for laminated glass 21 andthe second component for laminated glass 22 is removed by pressing theresulting product with pressure rollers, or by putting the product in arubber bag for vacuum-sucking. Then, the product is pre-bonded at about70° C. to 110° C. to give a laminate. Next, the laminate is put into anautoclave or is pressed, so as to be pressure-bonded with a pressure of1 to 1.5 MPa at about 120° C. to 150° C. Thus, the laminated glass 1 orthe laminated glass 11 can be obtained.

The laminated glass 1 and the laminated glass 11 can be widely used forcars, rail cars, aircrafts, vessels, buildings, and the like. Thelaminated glass can be used in applications other than these uses. Thelaminated glass 1 and the laminated glass 11 are preferably used aslaminated glasses for buildings or vehicles, and more preferably used aslaminated glasses for vehicles. The laminated glass 1 and the laminatedglass 11 can be used for windshields, side glass, rear glass, and roofglass of cars.

Hereinafter, the present invention will be described in more detailbased on examples. The present invention is not limited to theseexamples.

The following first plasticizer and the following second plasticizer areused in examples and comparative examples.

First Plasticizer:

Bis(2-butoxyethyl) adipate (corresponding to the first plasticizerrepresented by the formula (1A) wherein R21 and R26 each represent an-butyl group, R22 and R27 each represent an ethylene group, and m1 andm2 each represent 1, and n represents 4).

Bis[2-(2-butoxyethoxy)ethyl]adipate (corresponding to the firstplasticizer represented by the formula (1A) wherein R21 and R26 eachrepresent a n-butyl group, R22 and R27 each represent an ethylene group,and m1 and m2 each represent 2, and n represents 4).

Second Plasticizer:

Triethyleneglycol di-2-ethylhexanoate (3GO)

The following polyvinyl acetal resin A was synthesized.

Synthesis 1 Synthesis of a Polyvinyl Acetal Resin A

A reaction vessel provided with a stirrer was charged with ion-exchangewater (2700 ml), polyvinyl alcohol (300 g, average degree ofpolymerization: 3000, saponification degree: 87.2 mol %). The mixturewas molten by heating with stirring to give a solution. To the solution,35 wt % hydrochloric acid was added as a catalyst to a HCl concentrationof 0.6 wt %. After adjustment of the temperature to 15° C.,n-butylaldehyde (14.2 g) was added to the solution with stirring. Then,n-butylaldehyde (170 g) was added to cause precipitation of a polyvinylbutyral resin in the shape of white particles. In 15 minutes after theprecipitation, 35 wt % hydrochloric acid was added to a HClconcentration of 3.9 wt %. The solution was heated to 45° C. and agedfor three hours at 45° C. The solution was then cooled and neutralized.The polyvinyl butyral resin was washed with water and dried to give apolyvinyl butyral resin A.

The proportion of the high molecular weight component X (polyvinylbutyral resin) having an absolute molecular weight of at least 1 millionoccupying in the resulting polyvinyl butyral resin A was 14.5%. Theproportion of the high molecular weight component Y (polyvinyl butyralresin) having a molecular weight y of at least 1 million occupying inthe resulting polyvinyl butyral resin A was 18.2%. The hydroxyl contentwas 22.5 mol %. The acetylation degree was 12.8 mol %. Thebutyralization degree was 64.7 mol %.

Example 1

To the polyvinyl butyral resin A (100 parts by weight, carbon number ofthe acetal group: 4, average degree of polymerization: 3000, hydroxylcontent: 22.5 mol %, acetylation degree: 12.8 mol %, butyralizationdegree: 64.7 mol %) obtained in Synthesis 1 was added bis(2-butoxyethyl)adipate (50 parts by weight) as the first plasticizer. The mixture wassufficiently kneaded with a mixing roll, so that a composition for afirst layer was obtained. The polyvinyl butyral resin used was apolyvinyl butyral resin acetalized with n-butylaldehyde.

The resulting composition for a first layer was sandwiched between twofluororesin sheets via 0.1 mm-thick clearance plates. The laminate waspress-molded at 150° C. to give an interlayer film B1 (first layer)having a thickness of 0.1 mm.

To the polyvinyl butyral resin A (100 parts by weight, carbon number ofthe acetal group: 4, average degree of polymerization: 3000, hydroxylcontent: 30.5 mol %, acetylation degree: 1 mol %, butyralization degree:68.5 mol %) was added triethylene glycol di-2-ethylhexanoate (40 partsby weight). The mixture was sufficiently kneaded with a mixing roll, sothat a composition for a second layer was obtained. The polyvinylbutyral resin used was a polyvinyl butyral resin acetalized byn-butylaldehyde.

The resulting composition for a second layer was sandwiched between twofluororesin sheets via 0.35 mm-thick clearance plates. The laminate waspress-molded at 150° C. to give an interlayer film B2 (second layer)having a thickness of 0.35 mm.

An interlayer film B2, an interlayer film B1, and an interlayer film B2were stacked in the stated order to give a laminate having a multilayerstructure of Second layer/First layer/Second layer. The resultinglaminate was sandwiched between two fluororesin sheets via 0.8 mm-thickclearance plates. The laminated was press-molded at 150° C. to give amultilayer interlayer film B having a thickness of 0.8 mm.

Examples 2 to 8

The interlayer films B1 and B2 were produced in the same manner as inExample 1 using compositions for first and second layers prepared frompolyvinyl butyral resins and plasticizers shown in Tables 1 and 2. Usingthe interlayer films B1 and B2, multilayer interlayer films B wereobtained. Polyvinyl acetal resins used were polyvinyl acetal resinsacetalized by n-butylaldehyde. In each of Examples 2, and 6 to 8, thepolyvinyl acetal resin used for the first layer was the polyvinyl acetalresin A obtained in Synthesis 1.

Comparative Example 1

To the polyvinyl butyral resin A (100 parts by weight, carbon number ofthe acetal group: 4, average degree of polymerization: 3000, hydroxylcontent: 22.5 mol %, acetylation degree: 12.8 mol %, butyralizationdegree: 64.7 mol %) obtained in Synthesis 1 was added bis(2-butoxyethyl)adipate (50 parts by weight) as the first plasticizer. The mixture wassufficiently kneaded with a mixing roll, so that a composition wasobtained. The polyvinyl butyral resin used was a polyvinyl butyral resinacetalized by n-butylaldehyde.

The resulting composition was sandwiched between two fluororesin sheetsvia 0.8 mm-thick clearance plates. The composition was press-molded at150° C. to give an interlayer film A having a thickness of 0.8 mm.

Comparative Example 2

The interlayer films B1 and B2 were produced in the same manner as inExample 1 except that the kind and amount of the plasticizer in thecomposition for a first layer were changes in accordance with Table 2.Using the interlayer films B1 and B2, the multilayer interlayer film Bwas obtained. The polyvinyl acetal resin used for the first layer inComparative Example 2 was the polyvinyl butyral resin A obtained inSynthesis 1.

(Evaluation of Examples 1 to 8 and Comparative Examples 1 and 2)

The interlayer films and the polyvinyl acetal resins used in theinterlayer film of Examples 1 to 8 and Comparative Examples 1 and 2 wereevaluated for the following items (1) to (5) or (1) to (6). Examples 1to 4 and 6 to 8 and Comparative Examples 2 were evaluated also for thefollowing items (7) and (8).

(1) Sound Insulation: Temperatures T1 and T2 Each Indicating the MaximumValue of Tan δ at a Frequency of 1 Hz

Interlayer films B1-2 were obtained in the same manner as preparation ofthe interlayer films B1 of Examples 1 to 8 and Comparative Example 2,except that the thickness was changed to 0.8 mm for measurement of thetemperature indicating the maximum value of tan δ at a frequency of 1Hz. Interlayer films B2-2 were obtained in the same manner aspreparation of the interlayer films B2 of Examples 1 to 8 andComparative Example 2, except that the thickness was changed to 0.8 mm.The obtained interlayer films B1-2 and B2-2 were each cut into acircular shape having a diameter of 8 mm as an evaluation sample.

Each evaluation sample of the interlayer film B1-2 was examined for thedispersion of dynamic viscoelasticity with temperature under theconditions of a strain of 1.0%, frequency of 1 Hz, and heating rate of3° C./min with use of a viscoelasticity measuring device (“ARES”produced by Rheometrics) by a shearing method. Accordingly, thetemperature T1 indicating the maximum value of tan δ at a frequency of 1Hz was obtained. Each evaluation sample of the interlayer film B2-2 wasexamined for the dynamic viscoelasticity by the above method so that thetemperature T2 indicating the maximum value of tan δ at a frequency of 1Hz was obtained.

The interlayer film A of Comparative Example 1 was cut into a circularshape having a diameter of 8 mm as an evaluation sample. The evaluationsample was examined for the dynamic viscoelasticity by the above methodso that the temperature T1 indicating the maximum value of tan δ at afrequency of 1 Hz was obtained.

(2) Sound Insulation: Loss Factor

The interlayer film A or the multilayer interlayer film B was cut into asize of 30 mm length×320 mm width. The interlayer film A or themultilayer interlayer film B was sandwiched between two transparentfloat glass sheets (25 mm length×305 mm width×2.0 mm thickness). Theresulting product was held in a vacuum laminator at 90° C. for 30minutes for vacuum press to give a laminate. In the laminate, theinterlayer film A or the multilayer interlayer film B protruding fromthe glass sheets was trimmed so that the evaluation sample was prepared.The loss factor of the evaluation sample was determined using ameasuring device “SA-01”(produced by RION Co., Ltd.) at 20° C. by thecenter excitation method. The loss factor in a primary mode (around 1000Hz) of resonant frequencies of the obtained loss factor was evaluated.

(3) Slippage

The obtained interlayer film A or the multilayer interlayer film B wascut into a size of 150 mm length×300 mm width. The interlayer film A orthe multilayer interlayer film B was sandwiched between two transparentfloat glass sheets (150 mm length×300 mm width×2.0 mm thickness). Theresulting product was held in a vacuum laminator at 90° C. for 30minutes for vacuum press to give an evaluation sample. One face of theevaluation sample was fixed to a vertical plane and a float glass (150mm length×300 mm width×15 mm thickness) was attached to the other facewith a double-faced adhesive tape. A reference line was drawn on theside face of the laminated glass for measurement of the slippage. Thelaminated glass was left at 80° C. for 30 days. Then, the slippage oftwo glass sheets of the evaluation sample was measured.

(4) Evaluation on Bleeding

On the surface of the interlayer film A or the multilayer interlayerfilm B, five lines (8 cm length) were drawn with a red oil-based ink formarking. The marked interlayer film A or multilayer interlayer film Bwas placed to have its main surface positioned in a plane that is inparallel with the vertical direction. The marked interlayer film A ormultilayer interlayer film B was left for 2 to 4 weeks under steadytemperature and humidity conditions of 23° C. and a relative humidity of28%. The resulting interlayer film A or multilayer interlayer film B wasvisually observed to check if bleeding or dripping of the permanentmarker is present, and evaluated based on the following criteria.

[Evaluation Criteria of Moisture Resistance]

∘∘: No bleeding and no dripping was found in any of 5 lines after 4-weekstorage

∘: No bleeding and no dripping was found in any of 5 lines after 3-weekstorage, and bleeding or dripping was found in at least one of 5 linesafter 4-week storage

Δ: No bleeding and no dripping was found in any of 5 lines after 2-weekstorage, and bleeding or dripping was found in at least one of 5 linesafter 3-week storage

x: Bleeding or dripping was found in at least one of 5 lines after2-week storage

(5) Penetration Resistance

The obtained interlayer film A or the multilayer interlayer film B wascut into a size of 300 mm length×300 mm width. The interlayer film A ormultilayer interlayer film B was held for 24 hours under steadytemperature and humidity conditions of 23° C. and a relative humidity of28%. Then the interlayer film A or multilayer interlayer film B was thensandwiched between two transparent float glass sheets (300 mm length×300mm width×2.5 mm thickness, clear glass) to give a laminate. Theresulting laminate was temporarily bonded by using a heating roller at230° C. The temporarily-bonded laminate was bonded by using an autoclaveunder the conditions of 135° C. and a pressure of 1.2 MPa for 20 minutesto give a laminated glass.

The surface temperature of sheets of the obtained laminated glass (300mm length×300 mm width) used for the penetration resistance test wasadjusted to 23° C. Subsequently, according to JIS R 3212, a rigid spherehaving a mass of 2260 g and a diameter of 82 mm was dropped from aheight of 4 m on the center of each of six sheets of the laminatedglass. The laminated glass was considered to have passed the test if allthe six sheets of the laminated glass prevented the rigid sphere frompenetrating therethrough within five seconds after the rigid sphere hitthe sheets. The laminated glass was considered to have failed the testif three or less sheets of the laminated glass prevented the rigidsphere from penetrating therethrough within five seconds after the rigidsphere hit the sheets. In the case of four sheets, another six sheets ofthe laminated glass were tested again on the penetration resistance. Inthe case of five sheets, another sheet of the laminated glass wastested, and the glass was considered to have passed the test if theother sheet prevented the rigid sphere from penetrating therethroughwithin five seconds after the rigid sphere hit the sheet. In the sameway, a rigid sphere having a mass of 2260 g and a diameter of 82 mm wasdropped from heights of 5 m and 6 m on the center of each of six sheetsof the laminated glass to evaluate the penetration resistance of thelaminated glass.

(6) Bubble Formation Test A and Bubble Formation Test B (BubbleFormation State)

Each interlayer film was cut into a size of 30 cm length×15 cm width andstored for 10 hours at a temperature of 23° C. The both faces of theinterlayer film were embossed. The ten point height of irregularities ofthe embossment was 30 μm. In the cut interlayer film, through holes(diameter of 6 mm) were formed at four intersections of positions 8 cminside from the edges of the interlayer film in the lengthwise directionand positions 5 cm inside from the edges of the interlayer film in thecrosswise direction.

An interlayer film with through holes was sandwiched between twotransparent float glass sheets (30 cm length×15 cm width×2.5 mm thick)to give a laminate. The peripheral edge (2 cm width from each edge) ofthe laminate was heat-sealed to enclose air remaining in the embossmentand in the through holes. The laminate was press-bonded under theconditions of 135° C. and a pressure of 1.2 MPa for 20 minutes so thatthe remaining air is dissolved in the interlayer film. In this manner,the laminated glass sheets used in the bubble formation test A andbubble formation test B was prepared.

Bubble Formation Test A (Bubble Formation State)

Five sheets of the laminated glass used in the bubble formation test Awere prepared for each interlayer film. The prepared laminated glasssheets were left in an oven heated to 50° C. for 100 hours. The leftlaminated glass sheets were visually checked in a plan view fordetermination of the presence of bubble formation and the size of thebubbles. The bubble formation state evaluated based on the followingcriteria.

Bubbles generated in five laminated glass sheets was approximated byellipses. The area of the ellipse was determined as the bubble formationareas. The areas of the ellipses in five laminated glass sheets wereaveraged. The proportion (percentage) of the average value of the areasof the ellipses (bubble formation area) relative to the area (30 cm×15cm) of the laminated glass was calculated.

[Criteria for Evaluating the Bubble Formation State in the BubbleFormation Test A]

∘∘: No bubble formation was observed in all the five sheets.

∘: The proportion of the average value of the areas of the ellipses(bubble formation area) was less than 5%.

Δ: The proportion of the average value of the areas of the ellipses(bubble formation area) was at least 5% and less than 10%.

x: The proportion of the average value of the areas of the ellipses(bubble formation area) was at least 10%.

Bubble Formation Test B (Bubble Formation State)

A number of 30 sheets of the laminated glass to be used in the bubbleformation test B were prepared for each interlayer film. The preparedlaminated glass sheets were left in an oven heated to 50° C. for 24hours. The left laminated glass sheets were visually checked. The numberof laminated glass sheets in which bubble formation was visuallyobserved was checked and evaluated based on the following criteria.

[Criteria for Evaluating the Bubble Formation State in the BubbleFormation Test B]

∘∘: The number of glass sheets in which bubble formation was visuallyobserved was at most five.

∘: The number of glass sheets in which bubble formation was visuallyobserved was at least six and at most 10.

Δ: The number of glass sheets in which bubble formation was visuallyobserved was at least 11 and at most 15.

x: The number of glass sheets in which bubble formation was visuallyobserved was at least 16.

(7) Elasticity G′ Determined by the Testing Method A

Each polyvinyl acetal resin contained in the first layer of theinterlayer film for laminated glass of each of the examples andcomparative examples (polyvinyl acetal resin used in the first layer)(100 parts by weight) was sufficiently mixed and kneaded withtriethyleneglycol di-2-ethylhexanoate (3GO) as a plasticizer to give akneaded product. The resulting kneaded product was press-molded using apress molding machine to give a resin film A having an average thicknessof 0.35 mm. The resin film A was left under conditions of 25° C. and arelative humidity of 30% for two hours. Then, the viscoelasticity of theresin film A was determined using an ARES-G2 produced by TA INSTRUMENTS.A parallel plate with a diameter of 8 mm was used as a geometry. Themeasurement was performed under the conditions where the temperature waslowered from 100° C. to −10° C. at a cooling rate of 3° C./min at afrequency of 1 Hz and a strain of 1%. The peak temperature of the lossfactor in the measurement results was determined as a glass transitiontemperature Tg (° C.). The value of the elasticity G′(Tg+30) at (Tg+30)°C. and the value of the elasticity G′(Tg+80) at (Tg+80) ° C. were readfrom the measurement results and the glass transition temperature Tg.

The case where the ratio (G′(Tg+80)/G′(Tg+30)) was at least 0.65 wasdetermined as “∘”. The case where the ratio (G′(Tg+80)/G′(Tg+30)) wasless than 0.65 was determined as “x”.

(8) Elasticity G′ Determined by the Testing Method B

The interlayer film for laminated glass of each of the examples andcomparative examples was stored in a constant temperature and humidityroom (humidity of 30%(±3%), temperature of 23° C.) for a month. Then,the surface layer, intermediate layer and surface layer were detached sothat the intermediate layer was taken out. In a mold (2 cm length×2 cmwidth×0.76 mm thickness) positioned between two polyethyleneterephthalate (PET) films, the detached intermediate layer (1 g) wasplaced. After preheating at a temperature of 150° C. and a pressure of 0kg/cm² for 10 minutes, the intermediate layer was press-molded at 80kg/cm² for 15 minutes. The press-molded intermediate layer was placed ina handpress machine preliminary set to 20° C., and then pressed at 10MPa for 10 minutes to be cooled. One of the PET films was removed fromthe mold positioned between two PET films. The resulting mold was storedin a constant temperature and humidity room (humidity of 30%(±3%),temperature of 23° C.) for 24 hours. Then, the viscoelasticity of theinterlayer film was determined by using an ARES-G2 produced by TAINSTRUMENTS. A parallel plate with a diameter of 8 mm was used as ageometry. The measurement was performed under the conditions where thetemperature was lowered from 100° C. to −10° C. at a cooling rate of 3°C./min at a frequency of 1 Hz and a strain of 1%. The peak temperatureof the loss factor in the measurement results was determined as a glasstransition temperature Tg (° C.). The value of the elasticity G′(Tg+30)at (Tg+30)° C. and the value of the elasticity G′(Tg+80) at (Tg+80)° C.were read from the measurement results and the glass transitiontemperature Tg. The ratio (G′(Tg+80)/G′(Tg+30)) was also calculated.

The case where the ratio (G′(Tg+80)/G′(Tg+30)) was at least 0.65 wasdetermined as “∘”. The case where the ratio (G′(Tg+80)/G′(Tg+30)) wasless than 0.65 was determined as “x”.

(9) Measurement of the Absolute Molecular Weight and Molecular Weight y

(Measurement of the Absolute Molecular Weight)

The absolute molecular weight and the polystyrene-equivalent molecularweight for obtaining the high molecular weight component X and the highmolecular weight component Y mentioned in the synthesis 1 were valuesobtained as follows after detachment of the surface layer and theintermediate layer from the multilayer interlayer film.

For measurement of the absolute molecular weight, the multilayerinterlayer film was left in a constant temperature and humidity room(humidity of 30%(±3%), temperature of 23° C.) for a month. Then, thesurface layer and the intermediate layer were detached from themultilayer interlayer film. The detached intermediate layer wasdissolved in tetrahydrofuran (THF) to give a 0.1 wt % solution. Theresulting solution was analyzed using a Gel Permeation Chromatography(GPC) device (“RI: L2490, Autosampler: L-2200, Pump: L-2130, Columnoven: L-2350, Column: series of GL-A120-S and GL-A100MX-S” produced byHitachi High-Technologies Corporation). The GPC device was connectedwith a light scattering detector for GPC (“Model 1270 (RALS+VISCO)”produced by VISCOTEK) so that chromatograms by various detectors can beanalyzed. The peaks of the polyvinyl acetal component in thechromatograms by a RI detector and a RALS detector were analyzed usinganalysis software (OmniSEC). In this manner, the absolute molecularweight of the polyvinyl acetal resin in each elution time wasdetermined. The proportion of the area of the region where the absolutemolecular weight of the polyvinyl acetal resin is at least 1 millionoccupying in the peak area of the polyvinyl acetal resin which isdetected by using a RI detector was expressed in percentage.

The following equations are satisfied by the peak of each component inthe chromatogram:

A _(RI) =c×(dn/dc)×K _(RI)  Equation (1); and

A _(RALS) =c×M×(dn/dc)² ×K _(RALS)  Equation (2).

Here, c indicates a polymer concentration of the solution, (dn/dc)indicates a refractive index increment, M indicates the absolutemolecular weight, and K indicates the system's coefficient.

Specifically, polystyrene of known c, M, and (dn/dc) (Poly CAL(registered trade mark) produced by VISCOTEK, TDS-PS-NB Mw=98390,dn/dc=0.185) was used as a standard sample to give a 0.1 wt % solutionin THF. The system's coefficient of each detector was determined usingthe equations (1) and (2) based on the GPC measurement results of theobtained polystyrene solution.

The detached interlayer was dissolved in THF so that a solution in THFwas prepared. The absolute molecular weight M of the polyvinyl acetalresin was determined using the equations (1) and (2) based on the GPCmeasurement results of the obtained polyvinyl acetal resin solution.

For analysis of the intermediate layer (containing the polyvinyl acetalresin and the plasticizer), the concentration of the polyvinyl acetalresin of the polyvinyl acetal resin solution is needed to be obtained.The concentration of the polyvinyl acetal resin is calculated from thefollowing measurement results of the plasticizer content.

Measurement of the Plasticizer Content:

Plasticizer-THF solutions were prepared by dissolving the plasticizer inTHF to the plasticizer contents of 10 wt %, 15 wt %, 20 wt %, 25 wt %,30 wt %, 35 wt %, 40 wt %, 45 wt %, and 50 wt %. The GPC measurement wasperformed on each obtained plasticizer-THF solution so that the peakarea of the plasticizer was obtained. The peak area of the plasticizerrelative to the concentration of the plasticizer was plotted to give anapproximation straight line. Next, the GPC measurement was performed onthe solution in THF obtained by dissolving the intermediate layer inTHF. Based on the measurement result and the approximation straightline, the plasticizer content is determined from the peak area of theplasticizer.

(Determination of the Molecular Weight y)

In the same manner as the method for determining the absolute molecularweight, the polystyrene-equivalent molecular weight was determined bygel permeation chromatography (GPC). Based on the proportion of the areacorresponding to the region where the molecular weight is at least 1million occupying in the peak area (measurement result of GPC) detectedby a RI detector, the proportion (%) of the high molecular weightcomponent Y having a molecular weight y of at least 1 million occupyingin the polyvinyl acetal resin was calculated.

For determination of the polystyrene-equivalent molecular weight, GPCmeasurement was performed on polystyrene of known molecular mass as astandard sample. As a polystyrene standard sample (“Shodex StandardSM-105”, “Shodex Standard SH-75”produced by SHOWA DENKO K.K.), 14samples are used which have a weight average molecular weight of 580,1260, 2960, 5000, 10100, 21000, 28500, 76600, 196000, 630000, 1130000,2190000, 3150000, and 3900000. The approximation straight line obtainedby plotting the weight average molecular weight relative to the elutiontime indicated by the peak top of the sample peak is used as acalibration curve. The surface layer and the intermediate layer weredetached from the multilayer interlayer film left in a constanttemperature and humidity room (humidity of 30%(±3%), temperature of 23°C.) for a month. The detached intermediate layer was dissolved intetrahydrofuran (THF) to give a 0.1 wt % solution. The resultingsolution was analyzed by a GPC device so that the peak area of thepolyvinyl acetal resin in the intermediate layer was determined. Basedon the elution time and the standard curve of the polyvinyl acetal resinin the intermediate layer, the area corresponding to the region wherethe polystyrene-equivalent molecular weight of the polyvinyl acetalresin in the intermediate layer was at least 1 million was calculated.The area corresponding to the region where the polystyrene-equivalentmolecular weight of the polyvinyl acetal resin in the intermediate layerwas divided by the peak area of the polyvinyl acetal resin in theintermediate layer, and the resulting value was expressed in percentage(%). Accordingly, the proportion (%) of the high molecular weightcomponent Y having the molecular weight y of at least 1 millionoccupying in the polyvinyl acetal resin was calculated.

Tables 1 and 2 show the results.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ingredients of the Kind of theCarbon number of the acetal group 4 4 4 4 4 first layer polyvinylAverage degree of polymerization 3000 3000 3000 3000 2700 acetal resinThe hydroxyl content mol % 22.5 22.5 20.4 17.8 24.8 Acetylation degreemol % 12.8 12.8 7.1 1 17.5 Butyralization degree mol % 64.7 64.7 72.581.2 57.7 Amount of the polyvinyl acetal resin Parts by 100 100 100 100100 weight Kind and amount of Bis (2-butoxyethyl) adipate Parts by 50 5050 60 the first plasticizer weight Bis [2-(2-butoxyethoxy) ethyl]adipate Parts by 50 weight Kind and amount of Triethyleneglycol Parts bythe second plasticizer di-2-ethylhexanoate (3GO) weight Firstplasticizer:Second plasticizer (weight ratio) 10:0 10:0 10:0 10:0 10:0Ingredients of the Kind of the Carbon number of the acetal group 4 4 4 44 second layer polyvinyl Average degree of polymerization 3000 3000 30003000 3000 acetal resin The hydroxyl content mol % 30.5 30.5 30.5 30.530.5 Acetylation degree mol % 1 1 1 1 1 Butyralization degree mol % 68.568.5 68.5 68.5 68.5 Amount of the polyvinyl acetal resin Parts by 100100 100 100 100 weight Kind and amount Triethyleneglycol Parts by 40 4040 40 40 of the plasticizer di-2-ethylhexanoate (3GO) weight EvaluationSound insulation Temperature T1 indicating the maximum ° C. −1.24 1.223.21 1.21 −1.21 value of tan δ of the first layer Temperature T2indicating the maximum ° C. 30.5 30.5 30.5 30.5 30.5 value of tan δ ofthe second layer Loss tangent (20° C., around 100 Hz) 0.29 0.3 0.31 0.340.27 Slippage mm 0.4 0.4 0.7 0.8 0.9 Evaluation on bleeding ∘ ∘ ∘ ∘ ∘Penetration resistance 4 m Passed Passed Passed Passed Passed 5 m PassedPassed Passed Passed Passed 6 m Passed Passed Passed Passed PassedBubble formation test A (Bubble formation state) ∘∘ ∘∘ ∘∘ ∘∘ ∘∘ Bubbleformation test B (Bubble formation state) ∘ ∘ ∘ ∘ ∘ Testing method A:G′(Tg + 80)/G′(Tg + 30) ∘ ∘ ∘ ∘ — Testing method B: G′(Tg + 80)/G′(Tg +30) ∘ ∘ ∘ ∘ —

TABLE 2 Comp. Comp. Ex. 6 Ex. 7 Ex. 8 Ex. 1 Ex. 2 Ingredients of theKind of the Carbon number of the acetal group 4 4 4 4 4 first layerpolyvinyl Average degree of polymerization 3000 3000 3000 3000 3000acetal resin The hydroxyl content mol % 22.5 22.5 22.5 22.5 22.5Acetylation degree mol % 12.8 12.8 12.8 12.8 12.8 Butyralization degreemol % 64.7 64.7 64.7 64.7 64.7 Amount of the polyvinyl acetal resinParts by 100 100 100 100 100 weight Kind and amount of Bis(2-butoxyethyl) adipate Parts by 10 30 50 50 the first plasticizerweight Bis [2-(2-butoxyethoxy) ethyl] adipate Parts by weight Kind andamount of Triethyleneglycol Parts by 50 30 10 60 the second plasticizerdi-2-ethylhexanoate (3GO) weight First plasticizer:Second plasticizer(weight ratio) 1.7:8.3 5:5 8.3:1.7 10:0 0:10 Ingredients of the Kind ofthe Carbon number of the acetal group 4 4 4 4 second layer polyvinylAverage degree of polymerization 3000 3000 3000 3000 acetal resin Thehydroxyl content mol % 30.5 30.5 30.5 30.5 Acetylation degree mol % 1 11 1 Butyralization degree mol % 68.5 68.5 68.5 68.5 Amount of thepolyvinyl acetal resin Parts by 100 100 100 100 weight Kind and amountTriethyleneglycol Parts by 40 40 40 40 of the plasticizerdi-2-ethylhexanoate (3GO) weight Evaluation Sound insulation TemperatureT1 indicating the maximum ° C. −0.65 0.21 −4.21 −1.24 3.2 value of tan δof the first layer Temperature T2 indicating the maximum ° C. 30.5 30.530.5 — 30.5 value of tan δ of the second layer Loss tangent (20° C.,around 100 Hz) 0.29 0.32 0.36 0.32 0.23 Slippage mm 0.4 0.5 0.4 1.2 0.5Evaluation on bleeding ∘ ∘∘ ∘∘ x ∘ Penetration resistance 4 m PassedPassed Passed Failed Passed 5 m Passed Passed Passed Failed Passed 6 mPassed Passed Passed Failed Passed Bubble formation test A (Bubbleformation state) ∘∘ ∘∘ ∘∘ — ∘∘ Bubble formation test B (Bubble formationstate) ∘ ∘ ∘ — ∘ Testing method A: G′(Tg + 80)/G′(Tg + 30) ∘ ∘ ∘ — ∘Testing method B: G′(Tg + 80)/G′(Tg + 30) ∘ ∘ ∘ — ∘

The elasticity G′ of the resin film B (first layer) containing thepolyvinyl acetal resin of the first layer and the plasticizer of thefirst layer in amounts shown in Table 1 was measured after migration ofthe plasticizer among layers of the multilayer interlayer film.According to Tables 1 and 2, the ratio (G′(Tg+80)/G′(Tg+30)) of theresin film B and the ratio (G′(Tg+80)/G′(Tg+30)) of the resin Acontaining the polyvinyl acetal resin (100 parts by weight) contained inthe first layer and 3GO (60 parts by weight) are almost the same in theinterlayer films for laminated glasses of Examples 1 to 4, and 6 to 8,and Comparative Example 2.

Example 9

The polyvinyl butyral resin A obtained in Synthesis 1 (100 parts byweight, carbon number of the acetal group: 4, average degree ofpolymerization: 3000, hydroxyl content: 22.5 mol %, acetylation degree:12.8 mol %, butylarization degree: 64.7 mol %), bis(2-butoxyethyl)adipate (42 parts by weight) as the first plasticizer, andtriethyleneglycol di-2-ethylhexanoate (18 parts by weight) as the secondplasticizer were sufficiently mixed and kneaded with a mixing roll togive a composition. It is to be noted that the used polyvinyl butyralresin was the polyvinyl butyral resin acetalized by n-butylaldehyde.

The resulting composition was sandwiched between two fluororesin sheetsvia 0.8 mm-thick clearance plates. The laminate was press-molded at 150°C. to give a multilayer interlayer film A having a thickness of 0.8 mm.

Examples 10 to 12 and Comparative Example 3

The interlayer films A were produced by using the polyvinyl butyralresins and the plasticizers shown in Table 3 in the same manner as inExample 9. The used polyvinyl butyral resin was the polyvinyl butyralresin acetalized by n-butylaldehyde. The polyvinyl acetal resin used inthe first layer in each of Examples 10 to 12 and Comparative Example 3was the polyvinyl butyral resin A obtained in Synthesis 1.

Example 13

The polyvinyl butyral resin A obtained in Synthesis 1 (100 parts byweight, carbon number of the acetal group: 4, average degree ofpolymerization: 3000, hydroxyl content: 22.5 mol %, acetylation degree:12.8 mol %, butylarization degree: 64.7 mol %), bis(2-butoxyethyl)adipate (10 parts by weight) as the first plasticizer, andtriethyleneglycol di-2-ethylhexanoate (50 parts by weight) as the secondplasticizer were sufficiently mixed and kneaded with a mixing roll togive a composition for a sound insulation layer. The used polyvinylbutyral resin was the polyvinyl butyral resin acetalized byn-butylaldehyde.

The resulting composition for a sound insulation layer was sandwichedbetween two fluororesin sheets via 0.1 mm-thick clearance plates. Thelaminate was press-molded at 150° C. to give an interlayer film B1(first layer, sound insulation layer) having a thickness of 0.1 mm.

The polyvinyl butyral resin (100 parts by weight, carbon number of theacetal group: 4, average degree of polymerization: 3000, hydroxylcontent: 30.5 mol %, acetylation degree: 1 mol %, butylarization degree:68.5 mol %) and triethyleneglycol di-2-ethylhexanoate (40 parts byweight) were sufficiently mixed and kneaded with a mixing roll to give acomposition for protective layer. The used polyvinyl butyral resin wasthe polyvinyl butyral resin acetalized by n-butylaldehyde.

The resulting composition for a protective layer was sandwiched betweentwo fluroresin sheets via 0.35 mm-thick clearance plates. The laminatewas press-molded at 150° C. to give an interlayer film B2 (second layer,protective layer) having a thickness of 0.35 mm.

An interlayer film B2, an interlayer film B1, and an interlayer film B2were stacked in the stated order to give a laminate having a multilayerstructure including a protective layer/a sound insulation layer/aprotective layer (a second layer/a first layer/a second layer). Theresulting laminate was sandwiched between two fluororesin sheets via 0.8mm-thick clearance plates. The laminate was press-molded at 150° C. togive a multilayer interlayer film B having a thickness of 0.8 mm.

Examples 14 and 15

The interlayer films B1 and B2 were produced in the same manner as inExample 13 except that the amount of the plasticizer in the compositionfor a sound insulation layer was changed as shown in Table 4. Then,multilayer interlayer films were produced. In Examples 14 and 15, thepolyvinyl acetal resin used in the first layer was the polyvinyl butyralresin A obtained in Synthesis 1.

(Evaluation of Examples 9 to 15 and Comparative Example 3)

The interlayer films of Examples 9 to 15 and Comparative Example 3 wereevaluated with regard to the following items (1A) and (1B). In addition,the interlayer films of Examples 9 to 15 and Comparative Example 3 werealso subjected to (4) Evaluation on bleeding mentioned above. Theinterlayer films of Examples 13 to 15 and the polyvinyl acetal resinsused in the interlayer films were also subjected to (6) Bubble formationtest A and Bubble formation test B (bubble formation state), anddetermination of (7) Elasticity G′ by the testing method A and (8)Elasticity G′ by the testing method B.

(1A) Sound Insulation: Temperatures T1 and T2 Indicating the MaximumValue of Tan 5 at a Frequency of 1 Hz

The interlayer film A obtained in each of Examples 9 to 12 andComparative Example 3 was cut into a circular shape having a diameter of8 mm as an evaluation sample. The evaluation sample was examined for thedispersion of dynamic viscoelasticity with temperature under theconditions of a strain of 1.0%, frequency of 1 Hz, and heating rate of3° C./min with use of a viscoelasticity measuring device (“ARES”produced by Rheometrics) by a shearing method. Accordingly, thetemperature T1 indicating the maximum value of tan δ at a frequency of 1Hz was obtained.

The interlayer films B1-2 were obtained in the same manner as productionof the interlayer films B1 of Examples 13 to 15 except that thethickness was changed to 0.8 mm so that the temperature indicating themaximum value of tan δ at a frequency of 1 Hz was measured. In addition,the interlayer films B2-2 were obtained in the same manner as productionof the interlayer films B2 of Examples 13 to 15 except that thethickness was changed to 0.8 mm. The resulting interlayer films B1-2 andB2-2 were each cut into a circular shape having a diameter of 8 mm togive an evaluation sample.

The dynamic viscoelasticity of the evaluation sample using theinterlayer film B1-2 was determined by the above method, and thetemperature T1 indicating the maximum value of tan δ at a frequency of 1Hz was determined. The dynamic viscoelasticity of the evaluation sampleusing the interlayer film B2-2 was determined by the above method, andthe temperature T1 indicating the maximum value of tan δ at a frequencyof 1 Hz was determined.

(2A) Sound Insulation: Loss Factor

The resulting interlayer film A or multilayer interlayer film B was cutinto a size of 30 mm length×320 mm width. The interlayer film A ormultilayer interlayer film B was then sandwiched between two transparentfloat glass sheets (25 mm length×305 mm width×2.0 mm thickness) and heldin a vacuum laminator at 90° C. for 30 minutes for vacuum press to givea laminate. In the laminate, the interlayer film A or multilayerinterlayer film B protruding from the glass sheet was trimmed so thatthe evaluation sample was prepared. The loss factor of the evaluationsample was determined using a measuring device “SA-01”(produced by RIONCo., Ltd.) at 20° C. by the center excitation method. The loss factor ina primary mode (around 1000 Hz) of resonant frequencies of the obtainedloss factor was evaluated.

Tables 3 and 4 show the results.

TABLE 3 Comp. Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 3 Ingredients Kind of theCarbon number of the acetal group 4 4 4 4 4 polyvinyl Average degree ofpolymerization 3000 3000 2700 4000 3000 acetal resin The hydroxylcontent mol % 22.5 22.5 22.5 22.5 22.5 Acetylation degree mol % 12.812.8 12.8 12.8 12.8 Butyralization degree mol % 64.7 64.7 64.7 64.7 64.7Amount of the polyvinyl acetal resin Parts by 100 100 100 100 100 weightKind and amount Bis(2-butoxyethyl) adipate Parts by 42 6 30 of the firstweight plasticizer Bis[2-(2-butoxyethoxy)ethyl] adipate Parts by 42weight Kind and amount Triethyleneglycol di-2-ethylhexanoate (3GO) Partsby 18 18 54 30 60 of the second weight plasticizer Firstplasticizer:Second plasticizer (weight ratio) 7:3 7:3 1:9 5:5 0:10Evaluation Sound insulation Temperature T1 indicating the maximum value° C. −3.24 −1.24 2.11 0.21 3.21 of tan δ of the first layer Loss factor(20° C., around 100 Hz) 0.28 0.29 0.34 0.32 0.23 Evaluation on bleeding∘ ∘ ∘ ∘ ∘

TABLE 4 Ex. 13 Ex. 14 Ex. 15 Ingredients of the Kind of the Carbonnumber of the acetal group 4 4 4 sound insulation layer polyvinylAverage degree of polymerization 3000 3000 3000 acetal resin Thehydroxyl content mol % 22.5 22.5 22.5 Acetylation degree mol % 12.8 12.812.8 Butyralization degree mol % 64.7 64.7 64.7 Amount of the polyvinylacetal resin Parts by 100 100 100 weight Kind and amount ofBis(2-butoxyethyl) adipate Parts by 10 30 50 the first plasticizerweight Bis(2-(2-butoxyethoxy)ethyl) adipate Parts by weight Kind andamount of Triethyleneglycol di-2-ethylhexanoate (3GO) Parts by 50 30 10the second plasticizer weight First plasticizer:Second plasticizer(weight ratio) 1.7:8.3 5:5 8.3:1.7 Ingredients of the Kind of the Carbonnumber of the acetal group 4 4 4 protective layer polyvinyl Averagedegree of polymerization 3000 3000 3000 acetal resin The hydroxylcontent mol % 30.5 30.5 30.5 Acetylation degree mol % 1 1 1Butyralization degree mol % 68.5 68.5 68.5 Amount of the polyvinylacetal resin Parts by 100 100 100 weight Kind and amountTriethyleneglycol di-2-ethylhexanoate (3GO) Parts by 40 40 40 of theplasticizer weight Evaluation Sound insulation Temperature T1 indicatingthe maximum ° C. −0.65 0.21 −4.21 value of tan δ of the sound insulationlayer Temperature T2 indicating the maximum ° C. 30.5 30.5 30.5 value oftan δ of the protective layer Loss factor (20° C., around 100 Hz) 0.290.32 0.36 Evaluation on bleeding ∘ ∘∘ ∘∘ Bubble formation test A (Bubbleformation state) ∘∘ ∘∘ ∘∘ Bubble formation test B (Bubble formationstate) ∘ ∘ ∘ Testing method A: G′(Tg + 80)/G′(Tg + 30) ∘ ∘ ∘ Testingmethod B: G′(Tg + 80)/G′(Tg + 30) ∘ ∘ ∘

The elasticity G′ of the resin film B (first layer) containing thepolyvinyl acetal resin of the first layer and the plasticizer of thefirst layer in amounts shown in Table 1 was measured after migration ofthe plasticizer among layers of the multilayer interlayer film.According to Table 4, the ratio (G′(Tg+80)/G′(Tg+30)) of the resin filmB and the ratio (G′(Tg+80)/G′(Tg+30)) of the resin A containing thepolyvinyl acetal resin (100 parts by weight) contained in the firstlayer and 3GO (60 parts by weight) are almost the same in the interlayerfilm for laminated glasses of Examples 13 to 15.

EXPLANATION OF SYMBOLS

-   1 Laminated glass-   2A Interlayer film-   2 First layer-   2 a One face-   2 b The other face-   11 Laminated glass-   12 Interlayer film-   13 Second layer-   13 a Outer face-   14 First layer-   14 a One face-   14 b The other face-   15 Second layer-   15 a Outer face-   21 First component for laminated glass-   22 Second component for laminated glass

1. An interlayer film for laminated glass having a monolayer structurecomprising only a first layer, wherein the first layer contains apolyvinyl acetal resin that is a thermoplastic resin and a firstplasticizer represented by the formula (1):

in which R1 and R2 each represent an organic group containing at leastone ether bond and n represents an integer of 2 to 8, the first layerfurther contains a second plasticizer that is a diester compound, andthe polyvinyl acetal resin in the first layer has an acetylation degreeof at most 30 mol %.
 2. The interlayer film for laminated glassaccording to claim 1, wherein R1 and R2 in the formula (1) eachrepresent a group containing a carbon atom and an oxygen atom in a totalnumber of at most
 12. 3. The interlayer film for laminated glassaccording to claim 1, wherein R1 and R2 in the formula (1) each have atleast one ether bond structural unit represented by the formula (11):

or the formula (12):


4. The interlayer film for laminated glass according to claim 1,wherein, in the formula (1), R1 is a group represented by the formula(21):

in which R21 represents an alkyl group having 1 to 10 carbon atom(s),R22 represents an alkylene group having 1 to 10 carbon atom(s), and m1represents an integer of 1 to 5, and R2 is a group represented by theformula (26):

in which R26 represents an alkyl group having 1 to 10 carbon atom(s),R27 represents an alkylene group having 1 to 10 carbon atom(s), and m2represents an integer of 1 to
 5. 5. The interlayer film for laminatedglass according to claim 1, wherein the second plasticizer isrepresented by the formula (51):

in which R51 and R52 each represent an organic group having 5 to 10carbon atoms, R53 represents an ethylene group, isopropylene group, orn-propylene group, and p represents an integer of 3 to
 10. 6. Theinterlayer film for laminated glass according to claim 1, Wherein thefirst layer contains the first plasticizer and the second plasticizer ata weight ratio of 1:9 to 8.5:1.5.
 7. The interlayer film for laminatedglass according to claim 1, wherein the polyvinyl acetal resin in thefirst layer has a hydroxyl content of at most 25 mol %.
 8. Theinterlayer film for laminated glass according to claim 1, wherein thepolyvinyl acetal resin in the first layer is obtained by acetalizationof a polyvinyl alcohol having an average degree of polymerization of2700 to
 5000. 9. The interlayer film for laminated glass according toclaim 1, wherein the polyvinyl acetal resin in the first layer containsa high molecular weight component having an absolute molecular weight ofat least 1 million and the high molecular weight component accounts forat least 7.4% of the polyvinyl acetal resin in the first layer, or thepolyvinyl acetal resin in the first layer contains a high molecularweight component having a polystyrene-equivalent molecular weight of atleast 1 million and the high molecular weight component accounts for atleast 9% of the polyvinyl acetal resin in the first layer.
 10. Theinterlayer film for laminated glass according to claim 1, wherein, whenthe first layer is used as a resin film with a glass transitiontemperature of Tg (° C.) for measurement of the viscoelasticity, anelasticity G′(Tg+80) at (Tg+80) ° C. and an elasticity G′(Tg+30) at(Tg+30) ° C. have a ratio (G′(Tg+80)/G′ (Tg+30)) of at least 0.65. 11.The interlayer film for laminated glass according to claim 1, whereinwhen the viscoelasticity of a resin film containing 100 parts by weightof the polyvinyl acetal resin in the first layer and 60 parts by weightof triethylene glycol di-2-ethylhexanoate (3GO) as a plasticizer andhaving a glass transition temperature of Tg (° C.) for measurement ofthe viscoelasticity, an elasticity G′(Tg+80) at (Tg+80)° C. and anelasticity G′(Tg+30) at (Tg+30)° C. have a ratio (G′(Tg+80)/G′ (Tg+30))of at least 0.65.
 12. The interlayer film for laminated glass accordingto claim 1, wherein the polyvinyl acetal resin in the first layer isobtained by acetalization of a polyvinyl alcohol resin having an averagedegree of polymerization of more than
 3000. 13. The interlayer film forlaminated glass according to claim 1, wherein the polyvinyl acetal resinin the first layer has an acetylation degree of at least 8 mol %, or anacetylation degree of less than 8 mol % and an acetalization degree ofat least 68 mol %.
 14. The interlayer film for laminated glass accordingto claim 13, wherein the polyvinyl acetal resin in the first layer hasan acetylation degree of at least 8 mol %.
 15. The interlayer film forlaminated glass according to claim 13, wherein the polyvinyl acetalresin in the first layer has an acetylation degree of less than 8 mol %and an acetalization degree of at least 68 mol %.
 16. A laminated glasscomprising: a first component for laminated glass; a second componentfor laminated glass; an interlayer film between the first component forlaminated glass and the second component for laminated glass, whereinthe interlayer film includes the interlayer film for laminated glassaccording to claim 1.